Assembly Stress Research Articles

Statistical method of extracting assembly stresses in over-constrained solder-less press-fit pin technology for vibration reliability analysis

Abstract Solderless press-fit technology is increasingly favored over lead-free solder mountings due to cost-effective design benefits amid lead-free regulations. However, its over-constrained nature causes assembly issues and preload stress in pins, leading to fatigue failure under vibration. This paper extends previous research by presenting a method to evaluate the robustness of these assemblies under vibration-induced fatigue, considering assembly-induced stresses as static preload stress. The proposed statistical method uses Monte Carlo simulations to compute the distribution of pin failures due to fatigue, providing a comprehensive analysis that traditional worst-case FEA simulations cannot. This approach aids in identifying worst-case scenarios, predicting failure percentages, ranking designs, and improving design robustness through iterative feedback during the design phase.

On Self-Positioning and Self-Fixation of Parts Made of Alloys with Shape Memory Effect under Component Assembling

Introduction Violation of mutual positioning and fixation of parts worsens the operation of the equipment. Traditional approaches to solving the problem under consideration have been sufficiently studied: interchangeability of parts and the use of special equipment. Both methods involve a significant number of additional elements and assembly operations. Fixation is often provided by means of force fitting and welding. Disadvantages of these methods include assembly, residual and other stresses, engineering constraints, etc. To solve these problems, alloys with thermoelastic phase transformations are used, which provide shape memory effects (SME) to manifest themselves. This article describes, for the first time, self-positioning and self-fixation using the example of parts specially made from an alloy with SME. Materials and Methods. The pin element under pressing mandrels the blind hole of the cup and enters the seat. The alloy with SME was Ti-55.7wt%Ni. The temperature of the onset of its austenitic transformation was As = 95°C ± 5°C. The elemental composition was determined by a Shimadzu EDX-8000 X-ray fluorescence spectrometer, the phase composition — by a Shimadzu XRD-7000 diffractometer. The temperature was specified through differential scanning calorimetry. The range was 20–300°C, the heating rate was 5 deg/min. A Guide T120 thermal imager and a RangeVision DIY 3D scanner with structured illumination were used. After pressing the pin into the cup at different angles, the alignment and deviations between the axes of the cup and the pin were examined. Then, the cup was heated to 110–120°C, cooled, and control measurements were taken.Results. Values of the deflection angle after pressing were 0.2–11°. With a rigid structure and an installation angle of 0°, the pin deflected in the mounting hole by 0.2–0.5°. The axes shifted and did not intersect. The pin was not always completely pressed in. This indicated uneven deformation of the metal and different stress values around the hole. Such a unit would soon fail. The pin took the required position after heating the cup to 110–120°C (this temperature was higher than at the end of the reverse martensitic transformation). The angular deviation of the axes was noted to be 0.03–0.1°. The maximum misalignment (0.04 mm) corresponded to high positioning accuracy. Heating during the reverse martensitic transformation created internal stresses that returned the initial geometry of the cup. They also formed the forces that positioned and fixed the pin in the hole. That is, it is the parts that provide positioning and fixation (this is selfpositioning and self-fixation).Discussion and Conclusion. For self-positioning and self-fixation of parts due to the shape memory effect, it is necessary to avoid sharp transition lines between the surfaces of parts during design, select rounded corners or fillets, and get a clean surface without burrs. Self-fixation and self-positioning reduce defects and inaccuracies during assembly. The use of certain alloys increases the profitability of equipment production.

Methods of correction to extrinsic parameters in a stereoscopic vision with the assistance of two known-distance points.

Stereoscopic vision plays a significant role in a three-dimensional measurement. With the calibrated intrinsic and extrinsic parameters, stereoscopic vision can complete an accurate measurement. However, the extrinsic parameters are inevitably disturbed by variations in the environment, such as vibration and assembly stress, resulting in a huge measurement error. To overcome the problem, with the assistance of two known-distance points, this Letter proposes correction methods based on triangulation and differential geometry, respectively. The methods formulate the distance and solve the corrected extrinsic parameters. Simulated and actual experiments are carried out, and the results show high accuracy and stability of the proposed methods.

Co-exposure of bisphenol A and selenium deficiency induces pyroptosis via ROS/NLRP3 pathway in chicken spleen

Bisphenol A (BPA) is widely applied in plastic products, which will produce immunotoxicity to organisms after spilling in the environment, and become a kind of endocrine disruptor. Selenium (Se) is an essential trace element and plays an important role in maintaining redox homeostasis and immune function. BPA exposure and Se deficiency often occur together in livestock and poultry farming, however, studies on the effects of joint exposure on chicken immunotoxins have not been reported. Therefore, this study established a chicken spleen and MDCC-MSB1 cell model under the combined effects of BPA exposure or/and Se deficiency. Transcriptomic analysis showed that BPA exposure and/or Se deficiency induced differential enrichment of positive regulatory pathways such as NLRP3 inflammatory complex assembly, inflammatory response and cellular oxidative stress response. In the -Se+BPA group, pathological damage was significantly increased, Se content decreased, BPA accumulation, oxidative stress and pyroptosis. Meanwhile, the roles and mechanisms of oxidative stress and pyroptosis in BPA exposure or/and Se deficiency-induced splenic tissue injury were investigated by using IF and qRT-PCR methods. The results showed that joint BPA exposure with Se deficiency resulted in more significant changes in the above outcomes than one of them. The oxidative stress inhibitor NAC effectually reduced Se deficiency and BPA-induced oxidative stress and pyroptosis, further suggests that oxidative stress mediated Se deficiency or/and BPA-induced pyroptosis. This study revealed that BPA exposure and Se deficiency induced spleen pyroptosis in chickens via the ROS/NLRP3 pathway. These results provide the theoretical basis for the toxicity of BPA in poultry and enrich the toxicological mechanism of combined exposure of Se deficiency and environmental toxins.

Ultrasonic measurement method for three-dimensional assembly stress of aero-engine rotors

The precise measurement of three-dimensional stress in the rotor is a key means to ensure the assembly accuracy and operational safety of aero-engines. The unclear coupling influence mechanism of different directions of stress on ultrasonic propagation makes it challenging to establish a three-dimensional stress measurement model. This paper proposes a three-dimensional assembly stress measurement method for aero-engine rotors based on ultrasonic propagation time difference decoupling. The three-dimensional assembly stress is converted into the stress component parallel and perpendicular to the ultrasonic wave propagation direction in this method. The acoustoelastic equation including three-dimensional stress parameters is established based on the function model of different direction stress and ultrasonic wave propagation velocity. An innovative three-transducer stress measurement scheme is designed, which integrates ultrasonic wave transmitting and receiving transducers and time difference feedback transducers. The acoustoelastic equations in three propagation directions are constructed by rotating the transducer group to change the propagation direction of ultrasonic waves. Finally, the acoustoelastic equations are solved simultaneously to decouple the ultrasonic propagation time difference, thus achieving a three-dimensional assembly stress measurement of the aero-engine rotor. The experimental results show that the maximum deviation between the measured values and the simulation results in the x ,y, and z directions is 15.885 MPa, 14.113 MPa, and 17.093 MPa, respectively. This study provides effective theoretical and technical support for precisely measuring three-dimensional assembly stress in high-end equipment represented by aero-engines.

K29-linked free polyubiquitin chains affect ribosome biogenesis and direct ribosomal proteins to the intranuclear quality control compartment

Ribosome assembly requires precise coordination between the production and assembly of ribosomal components. Mutations in ribosomal proteins that inhibit the assembly process or ribosome function are often associated with ribosomopathies, some of which are linked to defects in proteostasis. In this study, we examine the interplay between several yeast proteostasis enzymes, including deubiquitylases (DUBs) Ubp2 and Ubp14, and E3 ligases Ufd4 and Hul5, and we explore their roles in the regulation of the cellular levels of K29-linked unanchored polyubiquitin (polyUb) chains. Accumulating K29-linked unanchored polyUb chains associate with maturing ribosomes to disrupt their assembly, activate the ribosome assembly stress response (RASTR), and lead to the sequestration of ribosomal proteins at the intranuclear quality control compartment (INQ). These findings reveal the physiological relevance of INQ and provide insights into mechanisms of cellular toxicity associated with ribosomopathies.

A cabin assembly optimization method based on force and position coordination analysis

In existing automated docking assembly solutions for aerospace products, segmented docking surfaces suffer from machining errors and deformation, making assembly difficult. The aim of this study was to reduce the internal stresses in cabin assembly and maintain sufficient assembly accuracy. A cabin assembly optimization method was developed based on force–position coordination analysis. To address the interference problem of the cabin flange surface, a penalty-function-based reweighting iterative approximation method was constructed based on the square-hole characteristics of the docking. In the assembly verification, mechanism calibration and measurement field iterative compensation optimized the mechanism pose, and the accuracy of the pose adjustment component and the cabin assembly stress were tested. The experimental results show that the method proposed can reduce the interference problem during the assembly of a flange face and optimize the assembly stress while achieving assembly accuracy. The results for accuracy and interference force after flange face assembly were obtained; however, no feedback on the analytical method was obtained through the experimental results. Therefore, it is necessary to test further the propositions investigated. The preassembly analysis method for large cabin assemblies proposed optimizes the cabin assembly accuracy and internal stress under the deformation state of the assembly surface.

Transcriptomic changes behind Sparus aurata hepatic response to different aquaculture challenges: An RNA-seq study and multiomics integration.

Gilthead seabream (Sparus aurata) is an important species in Mediterranean aquaculture. Rapid intensification of its production and sub-optimal husbandry practices can cause stress, impairing overall fish performance and raising issues related to sustainability, animal welfare, and food safety. The advent of next-generation sequencing technologies has greatly revolutionized the study of fish stress biology, allowing a deeper understanding of the molecular stress responses. Here, we characterized for the first time, using RNA-seq, the different hepatic transcriptome responses of gilthead seabream to common aquaculture challenges, namely overcrowding, net handling, and hypoxia, further integrating them with the liver proteome and metabolome responses. After reference-guided transcriptome assembly, annotation, and differential gene expression analysis, 7, 343, and 654 genes were differentially expressed (adjusted p-value < 0.01, log2|fold-change| >1) in the fish from the overcrowding, net handling, and hypoxia challenged groups, respectively. Gene set enrichment analysis (FDR < 0.05) suggested a scenario of challenge-specific responses, that is, net handling induced ribosomal assembly stress, whereas hypoxia induced DNA replication stress in gilthead seabream hepatocytes, consistent with proteomics and metabolomics' results. However, both responses converged upon the downregulation of insulin growth factor signalling and induction of endoplasmic reticulum stress. These results demonstrate the high phenotypic plasticity of this species and its differential responses to distinct challenging environments at the transcriptomic level. Furthermore, it provides significant resources for characterizing and identifying potentially novel genes that are important for gilthead seabream resilience and aquaculture production efficiency with regard to fish welfare.

Comparison influence of bilateral fluid pressure on fluid-solid coupling model of hydraulic torque converter structure

The main purpose of this paper is to explore the importance of external flow field circulation of hydraulic torque converter assembly in analysis. Compared with simply considering the internal flow field characteristics, it has influence on the internal flow field analysis, external characteristics and structural stress of hydraulic torque converter assembly. This paper models the flow path of the torque converter with different Schemes, the flow field pressures distribution on the impeller are analysed using computational fluid dynamics method (CFD). Scheme A adopts the traditional idea, which simply considering the influence of internal flow field on the performance. Scheme B contacts the external flow field especially including the auxiliary cavity, and comprehensively studies the influence of it on the performance. The results show that with the addition of an auxiliary chamber, the overall flow field pressure of the torque converter is lower than that without the auxiliary chamber. The external characteristics of the torque converter assembly were tested on experiment equipment, which has been verified that the CFD simulation results with the addition of the auxiliary chamber are closer to the experiment data, proving the accuracy of the method for the pressure simulation of flow field. On this basis, the stresses and deformations of the torque converter considering the auxiliary fluid chamber are compared and analysed in relation to the displacement limitations of the impellers. The results show that the maximum stress in the turbine is reduced by 57%–12% compared to the scheme A without considering the auxiliary fluid. In the case of special operating condition, the maximum stress was 137.06 MPa before considering the auxiliary fluid, while the maximum stress was 60.625 MPa after considering the auxiliary fluid, and the reduction is 57%. The effects of input speed, speed ratio and impeller structure on the stress and deformation were also analysed, and the results show that the impeller structure and input speed have a great influence on the stress and deformation.

Metabolomic Response of Thalassiosira weissflogii to Erythromycin Stress: Detoxification Systems, Steroidal Metabolites, and Energy Metabolism

Erythromycin, a macrolide antibiotic, is a prioritized pollutant that poses a high risk to environmental health. It has been detected in different environmental matrices and can cause undesired effects in aquatic organisms, particularly freshwater algae, which are primary producers. However, the impact of erythromycin on marine algae remains largely unexplored. Erythromycin has been reported to induce hormetic effects in the marine diatom Thalassiosira weissflogii (T. weissflogii). These effects are associated with the molecular pathways and biological processes of ribosome assembly, protein translation, photosynthesis, and oxidative stress. However, the alterations in the global gene expression have yet to be validated at the metabolic level. The present study used non-targeted metabolomic analysis to reveal the altered metabolic profiles of T. weissflogii under erythromycin stress. The results showed that the increased cell density was possibly attributed to the accumulation of steroidal compounds with potential hormonic action at the metabolic level. Additionally, slight increases in the mitochondrial membrane potential (MMP) and viable cells were observed in the treatment of 0.001 mg/L of erythromycin (an environmentally realistic level). Contrarily, the 0.75 and 2.5 mg/L erythromycin treatments (corresponding to EC20 and EC50, respectively) showed decreases in the MMP, cell density, and viable algal cells, which were associated with modified metabolic pathways involving ATP-binding cassette (ABC) transporters, the metabolism of hydrocarbons and lipids, thiamine metabolism, and the metabolism of porphyrin and chlorophyll. These findings suggest that metabolomic analysis, as a complement to the measurement of apical endpoints, could provide novel insights into the molecular mechanisms of hormesis induced by antibiotic agents in algae.

Logic-based mechanistic machine learning on high-content images reveals how drugs differentially regulate cardiac fibroblasts

Fibroblasts are essential regulators of extracellular matrix deposition following cardiac injury. These cells exhibit highly plastic responses in phenotype during fibrosis in response to environmental stimuli. Here, we test whether and how candidate anti-fibrotic drugs differentially regulate measures of cardiac fibroblast phenotype, which may help identify treatments for cardiac fibrosis. We conducted a high-content microscopy screen of human cardiac fibroblasts treated with 13 clinically relevant drugs in the context of TGFβ and/or IL-1β, measuring phenotype across 137 single-cell features. We used the phenotypic data from our high-content imaging to train a logic-based mechanistic machine learning model (LogiMML) for fibroblast signaling. The model predicted how pirfenidone and Src inhibitor WH-4-023 reduce actin filament assembly and actin-myosin stress fiber formation, respectively. Validating the LogiMML model prediction that PI3K partially mediates the effects of Src inhibition, we found that PI3K inhibition reduces actin-myosin stress fiber formation and procollagen I production in human cardiac fibroblasts. In this study, we establish a modeling approach combining the strengths of logic-based network models and regularized regression models. We apply this approach to predict mechanisms that mediate the differential effects of drugs on fibroblasts, revealing Src inhibition acting via PI3K as a potential therapy for cardiac fibrosis.

Hysteresis Stress, Strain and Penetration Analysis of Spur Gear Assembly for Various Sustainable Design

This paper considers and compares the hysteresis stress and strain and the penetration property of spur gear assemblies based on three unique designs. Spur gear plays an important part in mechanical structures, and any mechanical setup should consider the execution of such a mechanical component under distinct designs to improve its mechanical productivity and sustainability. To explore the ways in which the mechanical behaviour of the designs varies with the design configurations, we integrate simulation analysis with an experimental study. The outcomes of this paper indicate considerable differences in both hysteresis stress, strain distribution, and penetration behavior measurements between three designs. The paper explains the stated disparities by the unique geometric layouts and material characteristics of each design. Furthermore, it emphasizes that some of the examined designs have lower hysteresis losses and favourable stress and strain distributions, which positively affects the long-term performance of gear systems. Other designs, however, exhibit severe penetration and stress concentrations leading to rapid gear wear and likely premature failure. In distinguishing these events, the present study offers a valuable approach to the parameters that influence the performance of gear systems and aids in the improvement of the design methodology.

Candida albicans exhibits heterogeneous and adaptive cytoprotective responses to antifungal compounds.

Candida albicans, an opportunistic human pathogen, poses a significant threat to human health and is associated with significant socio-economic burden. Current antifungal treatments fail, at least in part, because C. albicans can initiate a strong drug tolerance response that allows some cells to grow at drug concentrations above their minimal inhibitory concentration. To better characterize this cytoprotective tolerance program at the molecular single-cell level, we used a nanoliter droplet-based transcriptomics platform to profile thousands of individual fungal cells and establish their subpopulation characteristics in the absence and presence of antifungal drugs. Profiles of untreated cells exhibit heterogeneous expression that correlates with cell cycle stage with distinct metabolic and stress responses. At 2 days post-fluconazole exposure (a time when tolerance is measurable), surviving cells bifurcate into two major subpopulations: one characterized by the upregulation of genes encoding ribosomal proteins, rRNA processing machinery, and mitochondrial cellular respiration capacity, termed the Ribo-dominant (Rd) state; and the other enriched for genes encoding stress responses and related processes, termed the Stress-dominant (Sd) state. This bifurcation persists at 3 and 6 days post-treatment. We provide evidence that the ribosome assembly stress response (RASTR) is activated in these subpopulations and may facilitate cell survival.

Stress measurement of aero-engine thin-walled catheter based on ultrasonic guided wave.

A pipeline system made of catheters is used for liquid-gas transportation in aero-engines. It is important to measure the residual stresses, such as the assembly stress in this system, as they influence performance and lifetime. Compared to other testing techniques, ultrasonic measurement methods based on acoustic-elastic effects can better solve problems. For the above requirements, this paper researches an aero-engine thin-wall catheter's assembly stress measurement method based on ultrasonic guided waves's acoustic, elastic effect. The propagation and dispersion characteristics of guided ultrasonic waves in the catheter were studied. Then, the excitation frequency, guided wave mode, and single-mode excitation mode of the simulation model were determined. Next, a finite element simulation model was established for simulation experiments. In order to reduce the influence of sampling rate and working environment noise on the measurement accuracy of assembly stress, the ultrasonic guided wave signal was processed by the wavelet threshold method. A good noise reduction effect was obtained by determining the wavelet base and the number of decomposition layers. Finally, an experimental platform was built to measure the assembly stress of thin-walled catheters. The maximum measurement error of the assembly stress of a thin-walled catheter was 21.1 MPa, which verified the feasibility of the measurement method. This study provides a promising method for accurately measuring the assembly stress of thin-walled catheters in aero-engines.

Research on automatic assembly technology of complex curved composite components

Sophisticated composite materials have a range of outstanding broad merits such as high particular strength, high specific stiffness, powerful designability, excellent tiredness resistance, excellent durability, are widely used in transportation, medical, electronics and other area. The assembly process of the composite surface components has large assembly stress, which affects the assembly accuracy. At the same time, the manual assembly cycle is elongated, the efficiency is low, and the quality stability is impoverished, which constraints the assembly mass and assembly power of the complex curved composite components. To improve the assembly power and carry out automatic assembly, this paper designs the automatic assembly technology scheme of the complex curved composite components, designs the automatic assembly scheme verification device, and conducts the automatic assembly test to verify the feasibility of the scheme.

Design and Optimization of Wheatstone Bridge Adjustment Circuit for Resistive Sensors

A novel Wheatstone bridge adjustment circuit with both rough-tuning and fine-tuning functions is designed for balancing Wheatstone bridge in this paper. Firstly, the parametric circuit structure is constructed to facilitate the design of rough-tuning and fine-tuning sub-circuit parameters; Secondly, the quantitative index of Wheatstone bridge imbalance is defined, and the parameter design flow of the rough-tuning sub-circuit, which consists of two sets of series-parallel-resistor (SPR) structures that are respectively connected in parallel with the two branches of one half-bridge, is given to directly weaken the initial bridge imbalance in the manufacturing stage. Theoretical analysis results show that the SPR structure can effectively approach any expected value and reduce the number of fixed resistor types. Thirdly, parameters of the fine-tuning sub-circuit, which consists of a resistor and a digital-to-analog converter (DAC), are optimized based on any expected adjustable range. By adjusting the DAC input to seek the middle value of an analog-to-digital converter output, indirectly eliminate the additional bridge imbalance caused by mechanical assembly stress, gravity, ambient temperature, and etc. in the application stage. Then the influence of the fine-tuning parameters on linear fitting coefficients of the output vs. input of the Wheatstone bridge is analyzed theoretically. The results show that the DAC output voltage only has a significant linear impact on the intercept coefficient, while its impact on the scale coefficient is negligible. Finally, the effectiveness of the adjustment circuit is verified on a six-axis force/torque sensor that is developed for an Experimental Module Manipulator in the Chinese Space Station.

Interference Assembly Stress of Wheel-Axle in B-type Subway

This paper aims to improve the reliability of train operation as well as to guarantee the safety of wheelset interference assembly. A finite element model of the wheel-axle interference fit is established with a metro B-type car as the research object. The finite element calculation software is used to simulate the static strength of the wheel-axle model under different working conditions, contact spots, and maximum/minimum interference. The effect of different interference and different working conditions on contact stress is studied. The study shows that the wheel meets the static strength requirements under all working conditions. The maximum equivalent stresses are located at the wheel hub bore under the maximum or minimum interference assembly. The full curved condition with maximum interference is the most dangerous condition among the working conditions.

Stress-based optimization of assembly surface mechanical properties oriented to stress-uniform assembly

Stress-uniform assembly is favorable for ensuring the precision and performance stability of precision electromechanical systems. Process compensation, assembly process optimization and assembly surface topography optimization are three typical ways to regulate the assembly stress distribution. Assembly surface mechanical properties optimization is a new and promising technique for achieving uniform stress distribution in assembled parts. This study takes that direction and investigates how variation in assembly surface material stiffness (i.e., Young's modulus) give rise to the variation in von Mises stress in assembled parts. To homogenize the von Mises stress distribution in assembled parts, the stress-uniform assembly-oriented material stiffness optimization model is constructed on the basis of finite element discretization. A stress-based material stiffness optimization method, which does not require sensitivity analysis, is developed by directly linking the amount of change in material stiffness to the value of von Mises stress. The feasibility and effectiveness of the stress-based assembly surface material stiffness optimization are demonstrated by a design case containing three elastic contact bodies, where both single-load and multi-loads conditions are considered. Some new phenomena during the assembly surface material stiffness optimization are also observed and explained.

Extracellular matrix assembly stress initiates Drosophila central nervous system morphogenesis.

Forces controlling tissue morphogenesis are attributed to cellular-driven activities, and any role for extracellular matrix (ECM) is assumed to be passive. However, all polymer networks, including ECM, can develop autonomous stresses during their assembly. Here, we examine the morphogenetic function of an ECM before reaching homeostatic equilibrium by analyzing de novo ECM assembly during Drosophila ventral nerve cord (VNC) condensation. Asymmetric VNC shortening and a rapid decrease in surface area correlate with the exponential assembly of collagen IV (Col4) surrounding the tissue. Concomitantly, a transient developmentally induced Col4 gradient leads to coherent long-range flow of ECM, which equilibrates the Col4 network. Finite element analysis and perturbation of Col4 network formation through the generation of dominant Col4 mutations that affect assembly reveal that VNC morphodynamics is partially driven by a sudden increase in ECM-driven surface tension. These data suggest that ECM assembly stress and associated network instabilities can actively participate in tissue morphogenesis.

Static Stress Analysis of Membrane Electrode Assembly (MEA) and Gasket in Proton Exchange Membrane Fuel Cell Stack Assembly Pressure

The proton exchange membrane fuel cell (PEMFC) system was an electrochemical device that generates electricity through the reaction of hydrogen and oxygen without combustion. Proton Exchange Membrane (PEM) stacks typically consisted of components combined into one unit and equipped with suitable clamping torque. This was to prevent reactant gas leakage and minimize the contact resistance between the gas diffusion medium and the bipolar plate. The combined components consisted of a bipolar plate with a flow field, current collector, membrane electrode assembly (MEA), endplate, and gasket. PEMFC performance was measured concerning its power output, which depends on temperature and the operating pressure. Various efforts had been made to determine the optimal compaction pressure and its distribution through simulations and experiments. Therefore, this research analyzed the static stress of membrane electrode assembly (MEA) and gasket in PEMFC stack assembly pressure. The components’ geometric dimensions and mechanical properties, such as endplates, current collectors, bipolar plates, MEAs, and gaskets, were combined for electricity. Pressure-sensitive film (Fuji measure film prescale) was also used to visualize contact pressure distribution between the MEA and the bipolar plate. The result showed that the color variation of the pressure film indicates the exact distribution of pressure entering the stacking design and the contact image. In conclusion, the detailed contact pressure distribution was an important influence on heat transfer processes and local electrochemical reactions in cell stacks.