Pin-bearing Strength Research Articles

Effect of edge distance-diameter ratio on pin-bearing strength of TC18 by laser melting deposition

Abstract This paper presents an experimental study on the pin-bearing characteristics of TC18 titanium alloy produced by laser melting deposition. Two types of specimens with edge distance-to-diameter ratios (e/D) were manufactured for pin-bearing tests. The S-Basis values of bearing strength are calculated based on statistical analysis of experimental data. The results indicate that the S-Basis value of bearing ultimate stress with e/D =1.5 specimens is 1648.12 MPa, and the S-Basis value of bearing ultimate stress is 1967.89 MPa for e/D =2.0 specimens. The S-Basis value of bearing ultimate stress for e/D=2.0 specimens is higher by 19.4% than that of e/D=1.5. The test result showed three different failure modes: shear-out, cleavage, and bearing. Each failure mode depends on the specific hole edge geometry adopted. The proportion of shear-out failure for e/D=1.5 samples is more than for e/D=2.0 specimens.

Implementation of Machine Learning in Predicting Pin-Bearing Strength of Aged and Nonaged Pultruded GFRP Composites

Implementation of Machine Learning in Predicting Pin-Bearing Strength of Aged and Nonaged Pultruded GFRP Composites

Analysis of surface roughness, temperature, short aging, and residual notched and bearing strengths in supported drilling of thin GFRP composites

This study aimed to analysis open‐hole tensile strength, pin-bearing strength, cutting temperature, and surface roughness of drilled thin glass fiber reinforced polymer composites. The specimens were clamped from both sides during drilling operations. The cutting temperature was measured using high resolution infrared camera. Surface roughness was evaluated by seven parameters to identify the most suitable ones. Multiple regression models were developed to predict critical thrust force (CTF), critical feed, and cutting temperature in drilling operations. The measurements indicate that the cutting temperature is higher than the matrix's glass transition temperature and hence, the surface roughness paramaters Ra, Rq and Ry are increased at the maximum cutting conditions by 57%, 51%, and 36% respectively. In contrast, the bearing strength improved by 13%. This peculiar phenomenon was deeply analyzed with the aid of short ageing effects on the post curing, which increase the crosslinking density within the composites and improve the matrix's capacity to efficiently transmit the loads to the reinforcing fibers. For the first time, the optimum cutting conditions were determined based on the optimum short ageing parameters (temperature and time). Supported drilling increases CTF by 23%, which can reduce machining time and manufacturing costs with fewer delamination concerns.

On the Pin-Bearing Strength of Additively Manufactured Polymer Parts

Due to the wide scope of applications of additive manufacturing (AM) in making final products, the mechanical strength of AM parts has become very important. Therefore, different tests are being developed to determine the structural integrity of three-dimensional printed components. In this respect, the pin-bearing test is designed to evaluate the response of a fastener, plate, and hole to stress. In this study, two different polymer materials were used to fabricate the samples utilizing the fused deposition modeling technique. Since the specimen width and hole diameter have effects on the pin-bearing strength and structural integrity of the parts, we prepared the specimens with four hole diameters to determine the influence of this ratio. A series of tensile tests were performed, and the stiffness and pin-bearing strength of additively manufactured specimens were determined. The preferred bearing failure mode was observed in several tested specimens. Subsequently, a scanning electron microscope investigation was conducted on the damaged area of the examined specimens to obtain insights into the damage mechanisms and failure behavior of the aforementioned specimens. We used digital image correlation technique to determine the strain field of dumbbell-shaped test coupons. The results of this research can be utilized for new designs of AM parts with a higher mechanical strength.

Pin-bearing mechanical behaviour of continuous reinforced Kevlar fibre composite fabricated via fused filament fabrication

In this study, the pin bearing behaviour of a 3D printed composite material with Kevlar reinforcement was analysed. Three different experimental tests were designed to determine the effects of fibre orientation, layer design, and fibre distribution along the specimen thickness. Furthermore, the pin-bearing strength and stiffness were analysed using statistical methods as analysis of variance. The results indicate a significant increase in bearing strength and stiffness for at least two fibre orientations, i.e. 0°and 90° with respect to the pin displacement. The results also highlight a no significant variation of strength and stiffness for parts produced adopting a mixed or single fibre orientation; finally, the findings do not indicate any significant influence of the fibre layer position inside the specimen, i.e. this parameter does not limit the freedom when designing a fibre-reinforced part.

Plain and threaded bearing strengths for the design of bolted connections with pultruded FRP material

Presented are results from testing 28 batches of 5 or 10 nominally identical specimens to characterise the laterally unrestrained pin-bearing strength when bolting is with and without thread. For the test series flange material is taken from a 254x254x9.53 mm Pultex® SuperStructural 1525 series shape. Strengths are measured with the Fibre Reinforced Polymer (FRP) material oriented at either 0° or 90° to the direction of pultrusion. Four steel bolt sizes of M10, M12, M16 and M20 are used, and when threaded there are different standard teeth (pitch) geometries. To remove this variable in a comparison with plain pin strengths a unique test series of 12 batches was carried out with three non-standard thread profiles. The effect on pin-bearing strength of having a threaded bolt is evaluated using mean and characteristic strengths, the latter determined in accordance with EN 1990. A key finding is that the proposed reduction factor of 0.6 in a forthcoming American LRFD standard to calculate a thread characteristic strength from the plain value is acceptable. Other findings are important to the determination of pin-bearing strength, and to us having knowledge and understanding to prepare a universal design procedure for resistances in bolted connections when the mode of failure is bearing.

Numerical Evaluation of Pin-Bearing Strength for the Design of Bolted Connections of Pultruded FRP Material

This paper presents finite-element predictions for the strength of a pultruded fiber-reinforced polymer (FRP) material subjected to pin-bearing loading with hole clearance. One of the distinct modes of failure in steel bolted connections is bearing. It is caused by the compression action from the shaft pressing into the laminate, and when there is no lateral restraint the mechanism observed at maximum load shows brooming for delamination failure. Each lamina in the glass fiber polyester matrix material is modeled as a homogeneous, anisotropic continuum and a relatively very thin resin layer is assumed to contain any delamination cracking between stacked layers. A cohesive zone model is implemented to predict the size and location of the initial delamination, as well as the load-carrying capacity in a pin-bearing specimen. Finite-element simulations (as virtual tests) are performed at the mesoscale level to validate the modeling methodology against experimental strength test results with delamination failure, and to show how pin-bearing strength varies with parameter changes. For an example of the knowledge to be gained for the design of bolted connections, the parameteric study in which the mat reinforcement is either continuous strand or triaxial (+45°/90°/−45°/chopped+45°/90°/−45°/chopped strand) shows the latter does not provide an increase in pin-bearing strength.

Effect of Hot-Wet Aging on the Pin-Bearing Strength of a Pultruded Material with Polyester Matrix

This paper presents test results to show the effect of hot-wet conditioning on the pin-bearing strength of a pultruded fiber reinforced polymer material. Knowledge of this strength property, taking account of any reduction over the service lives of structures, is required to reliably calculate bearing strength when designing bolted connections. Pin-bearing strength is determined using an in-house test method with batches of nominally identical specimens, cut from the web of a 203 x 203 x 9.53 mm wide flange shape. This shape is from the 1525 series of Creative Pultrusion Inc., having a polyester based matrix. Specimens were immersed prior to strength testing under water for 3000 hours at the constant temperature of 40° C. The paper discusses the accelerated aging protocol and its relation to service life, and an explanation is given to why the material was aged for an unknown number of service years. Variables in the test matrix are the direction of the bearing force (0°, 45° and 90° to the direction of pultrusion) and plain pin diameter (four sizes from 9.7 mm to 25.4 mm). Comparing aged pin-bearing strengths with equivalent strengths for non-aged material it is found that the average reduction in characteristic strength (calculated in accordance with Eurocode 0) of the 12 batches, is in the range of 18 to 31%. The extent of strength reduction is found to be independent of pin size, except when the diameter is 25.4 mm. For the 0o situation a comparison is made between the characteristic strengths for the four pin diameters determined using BS EN 1990:2002 and ASTM D7290 to show that the latter Weibull distribution values are lower, and by 4 to 18%.

Mechanical Properties of Highly Filled PVC/Wood-Flour Composites

The present article evaluates the effect of variation of WF on the tensile strength, modulus, and elongation at break. The pin-bearing properties usually correlate well with tensile properties. Tensile strength and pin-bearing strength decrease but tensile modulus increases on addition of WF. The tensile strength, pin-bearing strength, and mode of pin-bearing failure also depends on the void content. Increase in void content has a detrimental effect on all the mechanical properties. Wide variation is observed in impact strength because of unpredictable void content due to use of non-vented extrusion process. TGA indicates insignificant effect of WF on thermal stability of composites. Infrared spectroscopy indicates some interaction between PVC and WF.

Effects of Geometric Parameters on the Pin-bearing Strength of Glass/Polyphenylenesulphide Composites

In this experimental study, under conditions of static loading, load-bearing performance of pin connected multilayered (angle-ply) glass fiber-reinforced polyphenylenesulphide matrix composites with [(0°/90° )]4s and [(0°/90°)/ (+/—45 °)]2s stacking sequence was analyzed. The experiments were carried out according to the ASTM D953. The ratio of the distance between pin center and sample end, to pin diameter E/D; and the ratio of sample width to pin diameter W/D, were changed systematically during the experiments. From the results of the experiment, maximum bearing failure loads were obtained for [(0°/90°)/(+/—45°)] 2s lay-up with geometric parameters of D = 10 mm and W/D = 2. Macro images belonging to failure modes, which occurred as results of the tests were examined. In addition to this, from the fractographic examinations carried out with scanning electron microscope, it was concluded that the geometric parameters intimately affect fracture morphology.

Geometric parameters and chemical corrosion effects on bearing strength of polyphenylenesulphide (PPS) composites

The pin-bearing strength of polymer composites has been the focus of a significant research effort. In bolted composite structures, the presence of bolt holes induces high stress concentrations, which are hence recognized to be a source of damage developed during loading. In this study we aim to investigate the bearing performance of random oriented short fibre reinforced polyphenylenesulphide (PPS) composites which are widely used in various engineering applications. Both geometric parameters and chemical corrosion effects on the bearing performance of the material were investigated. It is concluded that the load bearing performance of the materials strictly depends on the geometric parameters of the joints. Chemical corrosion was also found an important environmental factor which was affecting the load bearing performance remarkably.

Pin and bolt bearing strength of fibreglass/aluminium laminates

Abstract An experimental investigation was carried out on a fibreglass/aluminium (FGA) laminate in order to characterise its behaviour under pin- and bolt-bearing conditions. In pin bearing, the limit width-to-diameter and edge distance-to-diameter ratios necessary to avoid unsafe failure modes were lower than those usually quoted for classical laminates. A simple model to design safe pin-bearing joints, previously proposed for fibre-reinforced plastics, was effective also for the FGA. The study of the failure modes suggested that the aluminium layers play a major role in determining failure. The latter was due to the shear buckling of the individual laminae, which were decoupled from each other by extensive delamination/debonding phenomena. Under bolt-bearing conditions, the features of the load–displacement curve allowed for the individuation of two bearing strengths, labelled as ‘damage-bearing strength’ and ‘failure-bearing strength’, respectively. The damage-bearing strength was substantially unaffected by the bolt torque, and was up to 20% higher than the pin-bearing strength. The failure-bearing strength slightly increased with increasing the clamping pressure, achieving values up to 85% larger than the pin-bearing strength. From the microscopic failure modes observed, a possible explanation for the two bolt-bearing strengths recorded was given.

Thermal Effects on the Pin-Bearing Behavior of IM7/PETI5 Composite Joints

Thermal effects on the pin-bearing behavior of an IM7/PETI5 composite laminate are studied comprehensively within this paper. Pin-bearing tests of several lay-ups at the operating temperatures of −129, 21, and 177°C are conducted to generate data on the effect of temperature changes on the pin-bearing behavior of the IM7/PETI5 material. A unique computational study investigating the factors influencing pin-bearing strength is performed for the [90,0]8s lay-up. A detailed three-dimensional finite element model is developed including the modeling of resin layers between plies in the laminate with a pin hole. Using a previously established technique, the pin-bearing problem was modeled assuming a rigid frictionless pin and restraining only radial displacements at the hole boundary. An original three-dimensional solution, where thermal residual stresses were combined with the state of stress due to pin-bearing loads was evaluated. The presence of thermal residual stresses were observed to intensify the interlaminar stresses predicted at the hole boundary in the pin-bearing problem. Furthermore, the research shows that changes in material properties drives pin-bearing strength degradation with increasing temperature. The thermal residual cure stresses then somewhat affect the extent that the pin-bearing strength changes with temperature. In general, thermal residual stresses were determined to be significant in affecting pin-bearing strength.

Pin-bearing strength of glass mat reinforced plastics

An experimental investigation was carried out, in order to find simple analytical methods for the prediction of pin-bearing strength of glass mat reinforced plastics fabricated by hand lay-up. The specimens tested exhibited different failure modes, consisting of net-tension, cleavage, and bearing, depending on the geometry adopted. The parameters affecting the bearing strength were the ratio of the specimen width to the hole diameter D, and the ratio of the edge distance to D. The maximum bearing strength was attained when a pure bearing failure happened. The latter was the only safe failure mode: after its occurrence, the joint was still able to support about 70% of its virgin strength. The experimental data obtained were used to assess a simple procedure for the calculation of the joint load carrying capacity, previously proposed. Since a large scatter was found in the bearing strength of the material, the data were analysed statistically, assuming a probability of failure varying according to a two-parameter Weibull distribution. An excellent agreement was found between the experimental results and the theoretical model. Similar conclusions were drawn applying the previous approach to the residual strength after bearing failure. A limited amount of tests was performed to verify the influence of possible damage induced during hole drilling on the bearing behaviour. It was found that a 20% decrease in bearing strength occurs when delamination is induced by inaccurate drilling. However, the residual bearing strength was substantially unaffected by the drilling damage.

Failure Process and Pin-Bearing Strength of Laminated Composites at Elevated Temperature

This paper is to investigate the failure process and pin-bearing strength of laminated composites under different temperatures. An incremental finite element code, based on the updated Lagrangian approach, was developed for determining the strains dis tribution of laminates under the consideration of the temperature dependent material prop erties. The quadratic failure criterion is adopted for failure predictions. Numerical results include the failure process, failure mode and ultimate bearing strength for two differ ent laminates, S-500 glass/polyester and graphite/epoxy, with three different lay-ups, [0°/45°/90°/-45°]s, [0° 2/ ±45°]s and [90°2/ ±45°]s, as well as with different end distances (e = d-4 d) and widths (W = 1.5 d-6 d). In order to verify the accuracy of the numerical calculations, the bearing strength model test is also made for understanding the effect of temperature on the failure behavior of the laminated composites with pin-loaded hole.

The Effect of Stacking Sequence on the Pin-Bearing Strength in Glass Fibre Reinforced Plastic

The pin-bearing strength of glass fibre reinforced plastic plates was measured using specimens possessing mid-plane symmetry and composed of eight layers, two each at 0° , 90° , and ±45° . The results suggest that placing the 90° layer (normal to the applied load) at or next to the surface increases the bearing strength. The ultimate failure mode was found to depend on stacking sequence.

Effect of Temperature and Moisture on Pin Bearing Strength of Composite Laminates

Effect of Temperature and Moisture on Pin Bearing Strength of Composite Laminates