Joint Design Parameters Research Articles

Bond behavior of CFRP-strengthened steel structures and its environmental influence factors: a critical review

Adhesively bonded carbon fiber-reinforced polymer (CFRP) systems have shown great promise for strengthening damaged steel structures, offering potential enhancements in the longevity of steel structures. However, the degradation of bond performance of CFRP under harsh environments remains a critical concern for researchers and engineers, as it may significantly impact the efficiency and durability of bonded CFRP strengthening systems. This paper presents a comprehensive review of the impact of key characteristics of bonded joints, such as the CFRP modulus, adhesive performance, bond length, adhesive layer thickness, and bond joint geometry, on the bonding performance of CFRP strengthening systems. Additionally, the influences of environmental factors, including elevated and sub-zero temperatures, moisture, corrosion, humidity, wet-dry cycles, ultraviolet radiation, and freeze-thaw cycles on the bond behavior, were also reviewed. By synthesizing and analyzing existing research insights into the effects of reinforcement materials, bond joint design parameters, and environmental factors on bonding performance, this review article attempts to enhance practitioners' understanding of bond behavior in this field and also provides guidance for future research.

Repair Analysis of Overlay Woven Fabric CFRP Laminates

The increase in aerospace composites usage for structural components demands advanced repair analysis. Overlay repairs of carbon fiber-reinforced polymer laminates offer an alternative that is easier to perform and less time-consuming to produce than the widely used tapered scarf repair and stepped lap. Composite specimen manufacturing was based on both twill carbon/epoxy prepreg and wet lay-up. The repair was performed with both prepreg and wet extra plies to the parent prepreg structure. However, the design of overlay joints must be carefully investigated to avoid generating stress concentration regions at free edges. This study examined specific extra ply terminations' impact on peak stresses in the adhesive bond line. Linear finite element analysis was performed to conduct a maximum principal stress study with a focus on three joint design parameters: ply material, overply effect, and stacking sequence. FEA accurately predicted experimentally observed responses and provided further insight into the failure behavior of the structure. Results showed that overlay joints have a strong sensitivity to ply material type, the number of overply, and stacking sequence. The introduction of overplies provided protection and stiffness at joint tips, and an overply material behavior was identified. The location of 0̊ plies in the composite laminates was highlighted as an important factor. The analysis was then extended to three-dimensional FE models for verification. In conclusion, results showed that high-stress concentration in overlay joints can be mitigated with the introduction of overplies and appropriate changes in joint design parameters to reduce stress peaks at joint tips and corners.

Analysis and Optimization of T Shape Weld Joint Using FEA

Abstract: The weld joints are used in various types of mechanical and civil engineering structures to strengthen the joints. The strength of T shaped weld joint significantly depends upon the design parameters of weld joint. The current research is intended to investigate the T shaped weld joint using techniques of Finite Element Analysis (FEA). The FEA analysis is conducted on T shaped weld joint using ANSYS simulation package. The optimization studies are conducted on T shaped weld joint to determine the effect weld joint parameters on induced deformation. From the optimization studies, the dimensions corresponding to weld height is determined for maximum and minimum deformation of T shaped weld joint.

A Tunable Metamaterial Joint for Mechanical Shock Applications Inspired by Carbon Nanotubes

The significant developments of additive manufacturing and especially 3D-printing technologies have broadened the application field of metamaterials. The present study aims at establishing the main design parameters of a novel 3D-printed polymer-based joint. The proposed joint can efficiently absorb impact energy, relieving the material components from extensive plastic deformations. The design of the machine element is inspired by the molecular structure of carbon nanotubes and appropriately adjusted in such a way that it has the ability to partially transform translational motion to rotational motion and, thus, provide axial structural protection from compressive shocks. The utilized material is a photosensitive resin that is typically utilized in 3D manufacturing processes. Experiments are utilized to characterize the mechanical performance of the raw material as well as the static compressive behavior of the joint. Finally, finite element simulations are performed to test the developed design under impact loadings characterized by different frequencies. The damping capabilities of the metamaterial-based joint are revealed and discussed.

The Healing Process of the Joints between Buffer Material Blocks and the Influence on Solute Migration

A set of thermo-hydro-mechanical coupling control equations was established, and the healing process of the joints between Gaomiaozi bentonite (GMZ01) buffer material blocks and the influence of the joint parameters were numerically simulated. The calculations consider the effect of joints on solute migration, the permeability and thermal conductivity of the buffer material, and the evolution of the healing effect. The effects of the joint design parameters, including the type, number, width, splicing form, and average dry density of the joint, are investigated. Studies show that, under an external water head, the joints will become hydraulic priority channels due to their higher permeability, which will shorten the saturation time of the blocks. As the bentonite gradually saturates, the swelling force compresses the joint material. This action improves the overall uniformity of the buffer material and reduces the priority channel effect. Meanwhile, the final average permeability and diffusion coefficient of the buffer material are found to mainly depend on the average dry density of the buffer material. The higher the average dry density of the buffer material is, the lower the final average permeability and diffusion coefficient are, whereas the distribution of joints and the block splicing are less affected by the average dry density of the buffer material. The findings of this study can provide a reference for the design of bentonite buffer material blocks in the repository.

Strength enhancement of bonded composite laminate joints reinforced by composite Pins

This paper presents an experimental and numerical investigation in the static strength enhancement of composite laminate Single Lap bonded Joints (SLJ), reinforced by pins made of Uni-Directional (UD) fibre reinforced plastic composite materials. Bonded lap joint specimens were experimentally tested in tension to obtain the failure loads and failure modes. The specimens were subsequently benchmarked against the hybrid version of the joint resulted from the introduction of composite Pins. The Pin reinforcement enhanced the hybrid single lap joint strength by an average of 19.1% increase. Numerical models generated were used for correlation with the experimental results. Numerical and experimental results observation indicated that increased strength of the hybrid bonded/Pinned joint was partly attributed to the load sharing between the adhesive and the Pin past the adhesive failure initiation as well as to the enhanced out-of-plane bending stiffness after the Pin introduction on the lap joint. Numerical investigations were performed as well with hybrid SLJ reinforced by composite pins versus designs employing metallic Pins. The simulations showed that for the investigated lap joint design parameters, the hybrid metallic pin joint failed at a higher failure load. Nevertheless, the hybrid joint utilizing the composite Pin could benefit from the enhanced corrosion resistance properties. In the case of applying a larger composite Pin diameter and/or rearranging the fibre orientation in the Pin, the hybrid SLJs could potentially achieve higher strength characteristics before the adhesive bond ultimate failure in relation to the steel Pin, as well as resulting to additional weight saving up to 46.9%.

Оценка точности и прочности модульной системы вспомогательного инструмента на основе профильных соединений

The purpose of the paper is to determine the values of elastic movements of mandrels when assessing the stress-strain state of modular constructions of a spindle-instrumental mandrel designed on the basis of conical detachable profile joints under static loading, and to estimate the accuracy and durability of a conical detachable profile joint designed for torque transmitting and featuring an equiaxial contour with a number of faces equal to three spindle-instrumental mandrel assemblies. The methods of numerical solution of elasticity theory problems including the finite-element method (FEM) as well as the methods of mathematical statistics and computer technology are used to study the stress-strain state of the modular system of an auxiliary tool based on profile joints. The paper provides the results of a complex research, the stress-strain state of modular structures of the multi-purpose machine-tool spindle assembly, namely: a modular system of an auxiliary tool based on profile joints with the equiaxial contour. The article analyzes the influence of design parameters of a conical profile joint, retaining pressure (with the fixation method by the magnitude of the assembly force), values of limiting external loads and friction forces on the accuracy and strength of spindle-instrumental mandrel joint with a profile mounting surface of the shank for actual dimensions of the modular design of the assembly. The values of elastic displacements of instrumental mandrel sections along the mounting length of the profile joint are determined with the use of the mathematical apparatus of the finite-element method based on spline approximation and a variation-energy principle of the displacement method of the elasticity theory. The calculation is performed of the values of elastic displacements of a mandrel and stresses in radial, normal and circumferential directions by the volume of the instrumental mandrel and spindle. Software in FEMAP 11.1 environment with NX NASTRAN has been applied for calculations. It has been determined that the values of elastic displacements of instrumental mandrel sections change nonlinearly and their value at the end face does not exceed 1.8 µm under the limiting external loads of the joint. Accordingly, the maximum values of the normal contact stresses in the extreme sections of the spindle do not exceed 7.71 MPa.

Beam‐column connections of concrete‐filled double steel tubular frame structures

SummaryFour types of concrete‐filled double steel tubular (CFDST) columns were introduced in this paper, which had the advantage of higher bearing capacity, stronger stiffness, and better fire‐resistant and explosion‐resistant performance. To research a reasonable form of beam‐column connection is the top priority in CFDST frame structures. After a brief historical background concerning the development of CFDST columns, this study conducted an investigation and comparison of several existing beam‐column connections. The constructional detail and force transfer mechanism of each beam‐column connection were analyzed according to the present research achievements. Several finite element models were established to discuss the various connection configurations and main factors affecting their behaviors. In general, connection design can take full advantage of the characteristic of double tubes in CFDST structure, so a series of construction improvements for joint design parameters in CFDST frame structures was proposed to improve the seismic performance and the relevant study for the future work was also discussed.

Multivariate analysis of high through-put adhesively bonded single lap joints

The goal of this research was to experimentally demonstrate the correlations between processing variables (adhesive type, bondline thickness, adherend thickness, surface pretreatment, overflow fillet) and effective strength in adhesively bonded single lap joints. While generalizations between effective strength and individual joint design parameters have been assumed for decades, the multifaceted interplay between parameters is complex and remains difficult to understand. Traditionally reported studies of the adhesive bond strength of single lap joints are often limited in the sample size populations needed to statistically probe concurrent design variables. To overcome sample size limitations a test matrix of 1200 single lap joints, partitioned by 96 unique fabrication conditions, was processed and tested using a workflow protocol orchestrated through a relational database. The enhanced pedigree and integrity enabled by using a relational database centered workflow allowed for multivariate principal component analysis of the joint design parameters, with all experimental data input available for peer audit. The results of this study revealed that the adhesive type biases the remaining joint configuration variables towards more influence with respect to either mechanical load or displacement to failure.

Optimisation study of tapered scarf and stepped-lap joints in composite repair patches

Stepped-lap repairs of composite structures can offer an alternative that is easier to perform and less time-consuming to produce than the widely used tapered scarf repair. However, the design of stepped-lap joints must be carefully investigated in order to avoid generating stress concentration regions. This study investigates the influence of joint parameters on peak stresses in the adhesive bondline in tapered scarf and stepped-lap joints. Linear finite element analysis was performed to conduct a parametric study with focus on six joint design parameters: ply thickness, adhesive thickness, taper angle, stacking sequence, overply layup, and overply lap length. Results showed that tapered scarf and stepped-lap joints have a strong sensitivity to ply thickness, taper angle, and stacking sequence. The introduction of overplies provided protection and stiffness at joint tips, and a critical overply lap length was identified. The location of 0° plies in the composite laminates was highlighted as an important factor. The analysis was then extended to three-dimensional FE models for verification. In conclusion, results showed that high stress concentration in stepped-lap joints can be mitigated with the introduction of overplies and appropriate changes in joint design parameters to reduce stress peaks at joint tips and step corners.

Load sharing in single-lap bonded/bolted composite joints. Part II: Global sensitivity analysis

Bonded/bolted joints in composites are potentially stronger and more durable than the underlying bonded and bolted joints separately. While recent experimental work has revealed that the most significant “across-the-board” improvements (compared to both constituent joints) are obtained when there is substantial load sharing between the adhesive and bolts, there is currently limited understanding of how load sharing works and how it can most effectively be achieved. In order to answer this question, this work presents an extensive global sensitivity analysis of a computational model of a single-bolt, single-lap composite joint containing an elastic–plastic adhesive. This model was previously developed and validated in part I of the paper. The objective of the sensitivity analysis was to quantify the relative importance of the different joint design parameters (factors) in load sharing. It was determined that adhesive yield strength is singularly the most important factor, by between 2 and 9 times depending on the level of load applied to the joint. The joint E/D ratio, adhesive hardening slope and adhesive thickness were found to be other significant factors influencing load sharing. For designs in which the adhesive overlap did not fully plasticise, no significant proportion (⩽10%) of the applied load was found to be transferred to the bolt.

Joint occurrence period of wind speed and wave height based on both service term and risk probability

Return periods calculated for different environmental conditions are key parameters for ocean platform design. Many codes for offshore structure design give no consideration about the correlativity among multi-loads and over-estimate design values. This frequently leads to not only higher investment but also distortion of structural reliability analysis. The definition of design return period in existing codes and industry criteria in China are summarized. Then joint return periods of different ocean environmental parameters are determined from the view of service term and danger risk. Based on a bivariate equivalent maximum entropy distribution, joint design parameters are estimated for the concomitant wave height and wind speed at a site in the Bohai Sea. The calculated results show that even if the return period of each environmental factor, such as wave height or wind speed, is small, their combinations can lead to larger joint return periods. Proper design criteria for joint return period associated with concomitant environmental conditions will reduce structural size and lead to lower investment of ocean platforms for the exploitation of marginal oil field.

BONDED JOINTS DESIGN AIDED BY COMPUTATIONAL TOOL DOI 10.5028/jatm.2012.04032912

In order to aid the design of bonded joints, a computational tool named System of Analysis for Joints (SAJ) was developed. The software can analyze single and double lap bonded joint with composite-composite or metal-composite materials as adherent parts. Thus, SAJ can calculate the stress distribution, loads and displacements. Their results were compared to finite element software (ABAQUSTM) and to specific composite analysis software (ESACompTM). After that, a study about the influence of joint design parameters on the mechanical behavior of the bonded joint was carried out. In regards to parametric study, SAJ leads to some conclusions, which can be used as a guide during the product design process. Therefore, aided by the computational tool, it is possible to perform a conceptual and preliminary design of bonded joints with more accuracy and varying many parameters (materials; fiber orientation and stacking sequence of the laminate; thickness; overlap length).

Computation of load factors in bolted connections

An accurate computation of the joint load factors is critical for the safe design of bolted connections. This study provides a four-step procedure for the direct computation of the joint load factors for a variety of bolt diameters, joint thicknesses, individual plate thicknesses, and plate material combinations. The finite element method was used to calculate the bolt and plate deformations necessary to directly compute the load factor for 4424 unique combinations of the four joint design parameters. The procedure developed in this study provides accurate estimates of the joint load factor over the entire range of the four joint design parameters. All 4424 joint designs originally analysed with the finite element method were recomputed using the proposed procedure. The root mean square error was found to be 0.58 per cent with a correlation coefficient between the load factors computed by using the original finite element analyses and the proposed procedure to be 0.9998.

B15 摩耗進行過程の連続観察による人工関節摺動部設計パラメータの検討(OS1 機械要素の強さと性能向上III)

B15 摩耗進行過程の連続観察による人工関節摺動部設計パラメータの検討(OS1 機械要素の強さと性能向上III)

Effect of Adhesive Thickness and Bonding Length on Behavior of Composite Adhesive Joints Subject to Torsion

Combined thermal and mechanical analyses were used to investigate the effect of joint design parameters such as the adhesive thickness and bonding length on stress distributions and torque capacities of tubular adhesive joints with composite adherends. The finite element analysis was employed to calculate the residual thermal stresses due to fabrication, and the mechanical stresses were analyzed using the nonlinear analysis of tubular adhesive joints. The analyses reveal that the stacking angle, adhesive thickness and bonding length have a significant influence on residual thermal stresses, and consequently failure modes and joint strengths.

Load transfer in hybrid (bonded/bolted) composite single-lap joints

The load transfer in hybrid (bolted/bonded) joints is complicated due to the difference in stiffness of the alternative load paths. The load distribution in hybrid composite single-lap joints has been predicted through use of a three-dimensional finite element model including the effects of bolt–hole contact and non-linear material behaviour. The effect of relevant joint design parameters on the load transferred by the bolt have been investigated through a finite element parameter study. Joint configurations where hybrid joining can provide improved structural performance in comparison to adhesive bonding have been identified. Experiments were performed to measure the distribution of load in a hybrid joint. A joint equipped with an instrumented bolt was used to measure the load transfer in the joint. The measured bolt load values were compared to predictions from the finite element model and the results were found to be in good agreement.

Seismic Behavior of Reinforced Concrete Column-Steel Beam Subassemblies and Frame Systems

In this paper, results are presented from tests of four reinforced concrete (RC) column-steel beam (RCS) subassemblies under large displacement reversals and dynamic analyses of RCS systems under various ground motions. The test specimens were designed following a strong column-weak beam philosophy and a deformation-based capacity design method for the connections. The effect of joint deformations on overall behavior of RCS frame systems was studied through a series of inelastic dynamic analyses performed on a six-story RCS frame with various joint modeling and design parameters. Results from this research show that RCS frame systems perform satisfactorily under seismic excitations. The test specimens showed a good strength and stiffness retention capacity with excellent energy dissipation up to displacement levels of approximately 5.0% drift. The joint deformation-based capacity design procedure was effective in controlling damage in the connection region, and thus forcing most of the inelastic activity to concentrate in the beam ends. From the analytical studies, it was found that joint deformations have a significant influence on maximum interstory drift of RCS frames. For the ground motions considered, an increase of up to 35% in maximum story drift was obtained when connection flexibility was considered in the analyses.

A two-term stress function approach to evaluate stress distributions in bonded joints of different geometries

The paper presents a method for the evaluation of the singular stress fields in bonded joints of different geometries. The stress distributions are represented by a two-term stress expansion, under the hypothesis that both the first and the second terms are in the variable separable form. The method is based on the stress function approach, where the formulation is completed analytically and the resulting set of ordinary differential equations is solved numerically. The capability of the formulation to account for the actual elastic properties of the substrates allows an accurate description of the singular stress field to be obtained even in the case of joints made of materials with comparable elastic properties. The influence of adhesive joint design parameters such as the type of joint, geometry and material properties on the generalized stress intensity factors will also be presented and discussed.

Modeling and evaluation criterion for thermocompression flip-chip bonding

A single joint finite element model (FEM) using a newly developed configuration independent evaluation criterion has been created, and experimentally verified, to provide more accurate predictions of bond formation based on the joint design and assembly process parameters. This model is based on the joint interface mechanics resulting from joint bump compression. Previous studies used a deformation criterion that depended on a specific joint configuration to evaluate the effectiveness of the expected bond. This limited the applicability of the model results to the joint design for which the deformation criterion had been experimentally determined. The technique reported in this research, uses finite element models to compute detailed distributions of stresses/strains at the interface of a joint when it is plastically deformed under compression. The evaluation criterion is defined to be the change in the differential area at the bonding interface, and is shown mathematically as follows: /spl Delta/A=/spl epsi//sub xx/+/spl epsi//sub yy//spl ges/(/spl epsi//sub xx/+/spl epsi//sub yy/)/sub crit/. Models using this criterion allow for the comparison of the effects of various joint design and manufacturing process parameters on the bond joint mechanics, and the resulting probable bond joint quality. A determination of the minimum deformation required for joint formation can be obtained for any design within specified limits.