Contact Parameters Research Articles

Preoperative strain ultrasound elastography can predict occult central cervical lymph node metastasis in papillary thyroid cancer: a single-center retrospective study.

To determine whether preoperative ultrasound elastography can predict occult central cervical lymph node metastasis (CCLNM) in patients with papillary thyroid cancer. This retrospective study included 541 papillary thyroid cancer patients with clinically negative lymph nodes prior to surgery between July 2019 and December 2021. Based on whether CCLNM was present on postoperative pathology, patients were categorized as CCLNM (+) or CCLNM (-). Preoperative clinical data, conventional ultrasound features, and ultrasound elastography indices were compared between the groups. Univariate and multivariate logistic regression analysis were performed to identify the independent predictors of occult CCLNM. A total of 36.60% (198/541) patients had confirmed CCLNM, while 63.40% (343/541) did not. Tumor location, bilaterality, multifocality, echogenicity, margin, shape, vascularity, capsule contact, extrathyroidal extension, aspect ratio, and shear wave elasticity parameters were comparable between the groups (all P > 0.05). Univariate analysis showed statistically significant differences between the two groups in age, sex, tumor size, calcification, capsule invasion, and strain rates ratio in strain ultrasound elastography (all P < 0.05). In multivariate logistic regression analysis, the independent predictors of occult CCLNM were age (OR = 0.975, 95% CI = 0.959-0.991, P = 0.002), sex (OR = 1.886, 95% CI = 1.220-2.915, P = 0.004), tumor size (OR = 1.054, 95% CI = 1.014-1.097, P = 0.008), and strain rates ratio (OR = 1.178, 95% CI = 1.065-1.304, P = 0.002). Preoperative strain ultrasound elastography can predict presence of occult CCLNM in papillary thyroid cancer patients and help clinicians select the appropriate treatment strategy.

Calibrating contact parameters of typical rotary tillage components cutting soil based on different simulation methods

This report analyzes the problem of complex soil movement patterns under the action of coupled forces, such as tension and shear, in agricultural processes and aims to improve the accuracy of contact parameters used in discrete element simulation studies of rototiller-soil interactions. This study focuses on the soil of Shihezi cotton field in the 8th division of Xinjiang and investigates the rotating tiller roller as a soil-touching component of tillage machinery. A combination of simulations and physical testing is used. We perform angle of repose tests and use edge detection, fitting, and other image processing methods to automatically, quickly, and accurately detect the soil accumulation and angle calibration of the contact parameters with soil particles. Additionally, soil slip tests are conducted to calibrate the contact parameters between the soil and the rotary blades. Optimization is achieved based on orthogonal simulations and the Box-Behnken response surface method using physically measured values as the target. A regression model of the stacking angle and rolling friction angle is established to determine the optimal combination of simulation contact parameters: between soil and soil, the recovery coefficient is 0.402, static friction coefficient is 0.621, and rolling friction coefficient is 0.078; between soil contact parts and soil, the recovery coefficient is 0.508, static friction coefficient is 0.401, and rolling friction coefficient is 0.2. Furthermore, the calibration parameters are selected as contact parameters for the discrete element simulation. By combining the above two simulation methods to analyze and compare the simulation process of cutting soil from rototiller roller parts to rototiller single blade parts, we obtained the changes in energy, cutting resistance, and soil particle movement at different depths of the soil cutting process. Finally, the average cutting resistance was used as an index for validation in the field tests. The measured value is 0.96 kN and the error of the discrete element simulation is 13%. This demonstrates the validity of the calibrated contact parameters and the accuracy of the simulation, which can provide a theoretical reference and technical support for the study of the interaction mechanisms between of tillage equipment parts and soil, as well as the design and optimization of these interactions in the future.

The NASA Ames legacy Mars global climate model: Radiation code error correction and new baseline water cycle simulation

Haberle et al. (2019) documented the status of the NASA Ames Legacy Mars Global Climate Model (GCM) and presented a baseline water cycle simulation. Since publishing that manuscript, we have found an error in the Legacy Mars GCM radiation code related to how the infrared cloud opacities were computed. Here we document this code error, its correction, how the corrected radiation code affects the simulated water cycle from Haberle et al. (2019), and what is required to produce a new realistic baseline water cycle simulation. We show that we can recover many, but not all, of the key aspects of the Haberle et al. (2019) baseline simulation by implementing a small change to the contact parameter, which is a microphysical parameter that affects the ease at which nucleation occurs. The fact that such a small change to the contact parameter can yield very different water cycles illustrates how sensitive the climate system is to cloud microphysical processes and highlights the need for future numerical and experimental study.

Fretting wear_lubrication of initially worn parts through tribo-induced anchorage of PTFE in wear scars, and tribochemical creation of graphene oxide

Fretting wear during launch operation is a well-known cause of anomalies in spacecraft. In this study, a CubSat satellite stayed stuck in its dispenser during the final preflight qualification test. So close to launch date, not a single part of the satellite could be replaced. A fretting test campaign has been carried out at tribometer scale to propose a solution to lubricate the damaged contacts. In depth expertise of the satellite allowed to determine the contact parameters. Damages and particles observed on the rail surfaces were successfully reproduced. The tests showed the appearance of a continuous flow of loose particles that either leave the contact or agglomerate inside it. Those agglomerating induced high friction and high adhesion. After contact opening and cleaning off the particles, lubrication was applied on the resulting damaged surfaces. Sprayed alkyl-phosphonic acid molecules and grease containing PTFE were selected to be tested as lubricant because they could be applied manually. PTFE accumulated in the damaged regions, protecting the surfaces from further damage while ensuring good lubrication. Sprayed alkyl-phosphonic acid molecules performed less. They however demonstrated in-situ tribochemical formation of a suspected graphene-oxide based lubricious 3rd body. Grease has been eventually chosen and the satellite successfully launched.

Hybrid SPH-FEM solver for metal cutting simulations on the GPU including thermal contact modeling

This paper presents a hybrid Smoothed Particle Hydrodynamics (SPH) – Finite Element Method (FEM) solver for metal cutting simulations on Graphics Processing Units (GPU). For the first time in chip formation simulation, the heat transfer between an SPH model of the workpiece, and a transient FEM temperature model for the cutting tool, is established. For validation, the performance of the modeled thermal contact between two numerical domains is compared with a commercial FEM software. The sensitivity of the implemented SPH-FEM contact parameters is investigated for the first time and further insights into the thermal modeling of cutting simulations are generated. Overall, the newly developed hybrid model saves the computational time on the cutting tool side in the pure SPH method and enables more efficient high-fidelity cutting simulations. By clearly defining the thermal contact at the tool-chip interface, the simulated tool surface temperature agrees well with the experimental measurements in the literature.

Wheel/rail adhesion and damage under different contact conditions and application parameters of friction modifier

Friction modifier (FM) is a newly developed third medium to control the service performance of wheel/rail. The wheel/rail performance is influenced by the wheel/rail contact conditions and FM application parameters. Therefore, the effects of FM application parameter and the wheel/rail contact parameters on the adhesion and damage behaviors of wheel and rail materials should be explored. In this study, the influences of application amount of FM, the wheel/rail contact stress and the creepage on the adhesion and damage behaviors were studied using a twin-disc machine. Results indicated that the increase in contact stress would reduce the wheel/rail minimum adhesion coefficient and effective holding time of FM. The increase in the creepage would increase the adhesion coefficient and reduce the holding time. Under the wheel/rail contact stresses of 800 and 1100 MPa, the application of FM could reduce wheel/rail wear and damage. But under 1500 MPa, FM could cause serious rail surface damages. Moreover, the surface crack propagation process of rail mainly included three stages: initial stage, transition stage and rapid propagation stage. The “oil wedge effect” was the main mechanism for aggravating the surface damages of rail under 1500 MPa.

Improving a technique to calculate strength of cylindrical rock samples in terms of uniaxial compression

Purpose is to improve analytical technique to calculate strength of cylindrical rock samples taking into consideration standard horizontal stresses. Methods. Mathematical modeling of cylindrical rock sample breakage under the truncated-wedge destruction was performed taking into consideration the standard horizontal stresses using four experimental characteristics (i.e. k being shear strength; fс and μ being contact and internal friction coefficients; and Е being elasticity modulus) as well as comparing the design strength with experimental data obtained in the process of uniaxial compression. Findings. The technique makes it possible to identify both maximum strength and residual strength of cylindrical rock samples using four indicators of properties which can be simply defined by experiment. Comparison of the analytical strength limits and experimental data, obtained in terms of uniaxial compression, supports the idea of high efficiency of the proposed technique. Originality. For the first time, analytical modeling of cylindrical rock sample breakage has been performed in terms of the truncated-wedge destruction taking into consideration the standard horizontal stresses as well as contact and internal friction parameters. Practical implications. The technique advantage is to apply promptly the calculation results in the context of industrial enterprises since their environment helps apply simple procedures to define indices of physiсomechanical characteristics of rocks for determination of stability of underground structures and reduction of energy consumption while disintegrating in open pits and mining and processing complexes.

Modeling the interaction between a new four-bar subsoiling mechanism and red soil using the improved differential evolution algorithm and DEM

Because of the poor subsoiling effects and high tillage resistances of small subsoiling machines when used on red soil in southern China, a new subsoiling mechanism based on functional bionics and an optimization method that employed an improved differential evolution (IDE) algorithm are proposed in this paper. The tillage performance was improved by causing the subsoiler to mimic the digging motion of a mole forefoot. The path synthesis of the subsoiling mechanism was solved by the IDE, and the tillage performance of the four-bar bionic subsoiling mechanism was evaluated by the discrete element method. First, the digging trajectory of the mole forefoot was mapped as the desired subsoiling trajectory. An optimization model for the path synthesis was established to minimize the position error between the desired subsoiling trajectory and the coupler curve of the mechanism; it was solved by the differential evolution algorithm with improvements in the mutation and crossover operations. It was found that the IDE could more rapidly search for a more accurate solution. The optimization results were used to design a bionic subsoiling mechanism that could mimic the digging trajectory of a mole forefoot. Second, the microscopic contact parameters among the soil particles were calibrated by soil accumulation and direct shear tests. In addition, a discrete element soil model was established that included dual coupling of variable contact models for the tillage layer and the plow pan. The tillage processes of an existing common subsoiling mechanism (CSM), the bionic subsoiling mechanism equipped with a common subsoiler (BSM&CS), and the bionic subsoiling mechanism equipped with a bionic subsoiler (BSM&BS) were analyzed by a joint ADAMS and EDEM simulation. The simulation results were analyzed according to established evaluation indexes for tillage performance. The comprehensive soil disturbance performance of the BSM&CS improved by 257.03% and its drag reduced by 10.87% from the CSM values, while the comprehensive soil disturbance performance of the BSM&BS improved by 312.78% and its drag reduced by 18.40% from the CSM values. Finally, the driving parameter combination for the BSM was optimized using the central composite design method.

Reflection and transmission of plane harmonicPwave at planar interface between elastic medium and frozen poroelastic medium

SUMMARYBased on the propagation theory of elastic waves in three-phase frozen poroelastic media and single-phase elastic media, the energy transmission problem of a plane harmonic P-wave incident at the planar interface between elastic medium and frozen poroelastic medium is studied. According to the boundary conditions at the planar interface, the analytical expressions of the transmission and reflection coefficients and energy ratios of the transmitted and reflected waves are derived. The relationship between the energy of plane harmonic P-wave incident on the planar interface between elastic medium and frozen poroelastic medium and the incident angle, frequency of incident wave, cementation parameters, porosity, saturation and contact parameters are investigated. The results show that the incident angle significantly affects the reflection and transmission energy ratios; the incidence frequency only has a large effect on the transmission energy ratios of the transmitted P2, P3 and S2 waves; the contact parameters have a relatively large effect on the reflected S wave and the transmitted P2, P3, S1 and S2 waves, but have a smaller effect on the reflected P wave and the transmitted P1 wave; cementing parameters, porosity, saturation has a great influence on the energy ratios.

Calibration Parameter of Soil Discrete Element Based on Area Difference Method

Existing calibration methods for contact parameters of soil discrete elements are primarily based on a single physical property of soil (e.g., natural accumulation angle and shear characteristics). To solve this limitation, a calibration method based on the area difference method was proposed in accordance with the actual operation effect of ridge and furrow opener. The typical clay loam in the middle and lower reaches of the Yangtze River (moisture content of 20.66% ± 1%) was used as the research object. The Hertz–Mindlin with JKR Cohesion contact model was selected, and the static friction factor and rolling friction factor between soil and 65Mn steel were determined by inclined plane mechanics method. Soil tank ridge and furrow opening experiments and quadratic orthogonal rotation combined tests were carried out. MATLAB software was used to carry out polynomial fitting and the constant integral solution to the ridge and the cross-sectional contour data of the furrow obtained from the measured and simulated ridge and furrow opening experiments to establish the regression model of area difference. The optimization function in Design-Expert software was adopted. The optimal parameter combination was obtained by optimizing the regression model with the minimum area difference as the target. Based on the above parameter combination, the relative error of cross-sectional area of the furrow that was obtained by simulation test and soil tank test was 9.15%. Finally, the comparison of the traction resistance of the simulation and the soil tank test at the stable working stage indicated that the relative error between the simulated value and the measured value was 10.4%, which is less than the acceptable error of 15% in general statistics and within a reasonable range. The results showed that the particle movement and mechanical properties of the soil simulation model were basically consistent with the actual soil after parameter optimization and calibration. In this study, a precise discrete element simulation model of the typical clay loam in the middle and lower reaches of the Yangtze River based on the area difference method was constructed, which lays a theoretical basis for later exploration of the interaction mechanism between the typical clay loam and the soil contact components in the middle and lower reaches of the Yangtze River.

Surface morphology, contact size and contact geometry effects on grease-lubricated fretting contacts

The fretting behaviour of AISI 52100 steel and low alloy steel under grease lubricated conditions is investigated. The friction behaviour is characterized by a high friction regime for the smallest displacement amplitudes below and next to the partial-slip transition whereas a low friction regime is stabilized above a threshold sliding amplitude when a lubricating tribofilm is generated in the interface. In order to quantify the influence of different contact parameters like surface roughness, contact size and contact geometry, a new fast simplified fretting methodology is introduced. This method allows scanning the entire fretting regime through a single experiment. An experimental comparison of smooth and rough surfaces shows that the effect of surface roughness influences the stability and the performance of the lubricating tribofilm. Experimental results obtained through changing the contact size of the cylinder-on-flat configuration permit identifying two contact size regimes. For small interfaces, the effective fretting sliding amplitude triggering the tribofilm activation is proportional to the contact size, whereas for large contacts this amplitude appears to be constant. The comparison with a punch-on-flat interface suggests that the lubrication activation is better captured by considering the peak pressure width rather than the nominal contact size.

Development of a pre-screening-method for the qualification of environmentally acceptable lubricants for stern tube systems—The evaluation of friction efficiency and scuffing capacity

Lubricants for stern tube systems are subject to increasingly stringent requirements in terms of environmental compatibility, as any lubricant leakage leads to contamination of the sea. As a result, interest in environmentally acceptable lubricants (EALs) is increasing. Biodegradable ester lubricants represent a possible alternative to conventional, mineral oil-based lubricants. In addition to environmental compatibility requirements, these ester lubricants must also meet tribological requirements. In this study, suitable tribometers were therefore combined in a pre-screening method to cost-effectively test lubricants for their tribological requirements (friction efficiency, wear protection and scuffing capacity). For this purpose, the contact parameters are transferred from the real conditions in the stern tube system’s journal bearing and from the standardized component tests (FZG for gears and FE8 for rolling bearings) to tribological model tests on a Mini-Traction-Machine (MTM, PCS Instruments). The result of the study is a method for the pre-screening of EALs under the application-related journal bearing and standardized component test conditions, respectively. The results show an influence of the lubricant composition on the friction efficiency in fluid friction as well as the transition point from fluid to mixed friction. Furthermore, an influence of the lubricant composition on the scuffing capacity could be shown. The results of friction efficiency and scuffing capacity confirm also a high reproducibility for those pre-screening tests.

Study of dynamic wedging performance of the multi-shape sprag clutch

The dynamic contact parameters such as contact force, contact stress and rotational speed fluctuate with time during the actual operation of a sprag clutch. To this end, ANSYS LS-DYNA is applied to simulate the dynamics of various types of sprag clutches with different wedge surfaces to obtain the curves of speed, contact force, and windup angle of each component during operation with time. The dynamic wedging performance of the all-phase type and the PCE (positive continuous engagement) type clutch is compared and analyzed, and the effect of the change of contact angle on the dynamic wedging performance of the sprag clutch with logarithmic and Archimedean spirals is investigated, and the dynamic wedging performance of the three types of sprag clutches is compared and analyzed to guide the design of multi-faceted sprag clutches.

Parameter Calibration and Systematic Test of a Discrete Element Model (DEM) for Compound Fertilizer Particles in a Mechanized Variable-Rate Application

In order to obtain accurate discrete element simulation model (DEM) parameters of compound fertilizer and solve the problem of challenging measurement of contact parameters of compound fertilizer particle, simulation calibration test was carried out by using EDEM simulation soft-ware. This study measured the intrinsic parameters and contact parameters of compound fertilizer particles through physical tests and established a simulation model that corresponds with the actual situation to calibrate the contact parameters of compound fertilizer particles. By using the Blackett-Burman test, the parameters that had a significant impact on the compound fertilizer’s resting angle were determined by the fertilizer-fertilizer collision recovery coefficient, fertilizer-fertilizer rolling friction coefficient, and fertilizer-steel static friction coefficient. Utilizing the steepest ascent test, the ideal value intervals for the three key parameters were identified. Box-Burman response surface analysis was used to establish and optimize the regression model of the rest angle and significant parameters. With the actual rest angle as the target value, the best combination of significant parameters was found, which was used for the simulation verification test. The simulated rest angle was 20.61°, whereas the real rest angle was 19.95°, with a relative error of 3.31%. The results demonstrate that the calibration parameters are essentially accurate representations of the real characteristics, which can serve as a reference point for simulation research and optimization design of variable fertilizer spreader.

Parameter Calibration of Cabbages (Brassica oleracea L.) Based on the Discrete Element Method

The discrete element parameters of cabbages (Brassica oleracea L.) were calibrated for the design and parameter optimization of a cabbage harvester. The cabbage model was created based on the study of cabbage material characteristics and the simulation model parameters of cabbage were calibrated. The intrinsic parameters and partial contact parameters of cabbages were obtained by direct measurement. The cabbage accumulation angle was determined by a plate drawing test. Through the steepest ascent test and the orthogonal rotation combination test, a regression model of the cabbage accumulation angle error was established. The optimal contact parameters between the cabbages were obtained by the minimum error modeling. These calibrated parameters were applied in the verification test, and the results indicated that the error between the simulated and measured values of the cabbage accumulation angle was only 1.63%, which demonstrated that the results were dependable. This study can provide a theoretical support for designing and optimizing the parameters of cabbage harvesting machines with the discrete element method (DEM).

Generalised Kelvin contact models for DEM modelling of asphalt mixtures

ABSTRACT Rigid particle models based on the discrete element method (DEM) have been adopted to model creep, fracture, and the viscoelastic behaviour of asphalt mixtures considering an irregular micro-structure and particle contacts. Within a DEM framework, the Burgers contact model, which is known to have a narrow frequency and temperature range, is usually adopted to model viscoelastic properties. In this study, a new explicit three-dimensional generalised Kelvin (GK) contact model formulation for the DEM model is proposed for asphalt materials. The model is implemented following two different methodologies (GK 1 and GK 2 ). The models are validated in uniaxial tension-compression sinusoidal tests for predicting the dynamic modulus ( | E ∗ | ) and phase angle (ϕ) of these composites at a frequency range of 1–10 Hz at 20 ∘ C. Four mixtures are investigated based on the modelling of their mastic. The influence of the GK contact parameters on the dynamic response of mastics is assessed. Results show that κ m has an important influence on both rheological properties and that η m can be used for small adjustments focussing on the predicted phase angle. Moreover, it is shown that a viscoelastic contact model should be adopted to simulate aggregate-to-mastic contacts in mixtures. As expected, the response obtained for both GK models is the same but the simulations with the GK 1 are 14% faster. In addition, the response predicted with the proposed GK contact model is compared with the response predicted with a Burgers contact model. The DEM predictions obtained for the GK model are more accurate. For mastics, the average errors for | E ∗ | and ϕ when adopting the GK model (Burgers) are 2.40% (3.46%) and 3.64% (4.17%), respectively. For mixtures, the average errors for | E ∗ | for the GK model (Burgers) are 7.00% (7.92%). The proposed contact model greatly enhances the DEM ability to simulate the viscoelasticity of asphalt materials.

Research on the effect of the cone-in-cone insert on the discharge behaviour of conical silo

During silo unloading, the reliability of the silo can be improved by adding inserts with appropriate parameters to improve the flow pattern. In this study, DEM was used to study the influence of the cone-in-cone insert parameters on the silo discharge behaviour. The contact parameters were measured through a series of experiments, and the DEM model was established and verified. Furthermore, the silo unloading process with different insert parameter combinations was simulated, and the flow patterns were characterized by the Mass flow index (MFI). The simulation results revealed that the insert angle β and the height from the silo port H1 significantly affect the flow pattern. To realize the mass flow, H1, H2 and D2 should be reasonably selected under the β > 135°. After adding an insert with the β > 130°, the normal pressure along the silo wall was evenly distributed, and there was less wear.

Identifiability of soft tissue constitutive parameters from in-vivo macro-indentation

Reliable identification of soft tissue material parameters is frequently required in a variety of applications, particularly for biomechanical simulations using finite element analysis (FEA). However, determining representative constitutive laws and material parameters is challenging and often comprises a bottleneck that hinders the successful implementation of FEA. Soft tissues exhibit a nonlinear response and are commonly modeled using hyperelastic constitutive laws. In-vivo material parameter identification, for which standard mechanical tests (e.g., uniaxial tension and compression) are inapplicable, is commonly achieved using finite macro-indentation test. Due to the lack of analytical solutions, the parameters are commonly identified using inverse FEA (iFEA), in which simulated results and experimental data are iteratively compared. However, determining what data must be collected to accurately identify a unique parameter set remains unclear. This work investigates the sensitivities of two types of measurements: indentation force-depth data (e.g., measured using an instrumented indenter) and full-field surface displacements (e.g., using digital image correlation). To eliminate model fidelity and measurement-related errors, we employed an axisymmetric indentation FE model to produce synthetic data for four 2-parameter hyperelastic constitutive laws: compressible Neo-Hookean, and nearly incompressible Mooney-Rivlin, Ogden, and Ogden-Moerman models. For each constitutive law, we computed the objective functions representing the discrepancies in the reaction force, the surface displacement, and their combination, and visualized them for hundreds of parameter sets, spanning a representative range as found in the literature for the bulk soft tissue complex in human lower limbs. Moreover, we quantified three identifiability metrics, which provided insights into the uniqueness (or lack thereof) and the sensitivities. This approach provides a clear and systematic evaluation of the parameter identifiability, which is independent of the selection of the optimization algorithm and initial guesses required in iFEA. Our analysis indicated that the indenter’s force-depth data, despite being commonly used for parameter identification, was insufficient for reliably and accurately identifying both parameters for all the investigated material models and that the surface displacement data improved the parameter identifiability in all cases, although the Mooney-Rivlin parameters remained poorly identifiable. Informed by the results, we then discuss several identification strategies for each constitutive model. Finally, we openly provide the codes used in this study, to allow others to further investigate the indentation problem according to their specifications (e.g., by modifying the geometries, dimensions, mesh, material models, boundary conditions, contact parameters, or objective functions).

Measurement of vibro-acoustic noise of drum brake under various contact conditions

Drum brakes are vital safety components, widely used in automobiles due to their greater availability and quick replaceability compared to disc brakes. Since automobiles are used in all weather conditions, the braking performance also changes accordingly. Penetration of water, oil, and dust between the brake lining and the drum directly affects the contact parameters. These critical contact parameters (such as friction coefficient, contact damping, and stiffness) in turn affect the dynamic and acoustic responses of the nonlinear system. In this paper, the variation in the vibro-acoustic characteristics of a drum brake due to the presence of water, oil, and dust on the brake lining is studied experimentally by measuring the radiated acoustic signals and the system response. The braking performance under different conditions is quantified based on the system response while the acoustic behaviour of the system is studied using the acoustic measurements. This study would help in determining the safety of the automobile even under such abnormal braking conditions. Further, the acoustic measurements can be used to assess the contact condition of the braking system. It is envisaged to develop an improved health monitoring system for drum brakes.

Influence of contact parameters on the radiated noise from an automotive drum brake

Drum brakes are the major source of noise and vibrations in the automobile as the drum acts as a significant source of the noise. High-frequency noises are generated at the interfacial contact between the brake shoe and brake drum. Hence, the variation in the contact parameters (friction, contact stiffness, and contact damping) will significantly affect the vibro-acoustic noise emanating from the drum brake. The current work quantifies the variation in vibro-acoustic noise due to an asymmetry in the contact of leading and trailing shoes with the drum. The overall sound pressure level is estimated numerically using a finite element model of the drum brake. Multiple spring-like components in parallel between the brake shoe and the drum imitate the contact in real drum brakes. The numerical model predicts the noise generated by a symmetric system (without any asymmetry defects) and a system with controlled asymmetric defects introduced into the model. The results show that the overall sound pressure level is a strong function of the contact parameters. The current research is envisioned to better the selection of contact parameters and hence the drum and shoe properties.