Tensile Strength Distribution Research Articles

Multi-objective reliability-based optimization for cooling channel of a UHSS hot-stamping die

A multi-objective reliability-based design optimization was proposed to optimize the cooling system parameters with regard to cooling efficiency and structure reliability. To address the contradictions between cooling capacity and mechanical strength of hot-stamping die, energy balance principle and simplified mechanical models were investigated. The multi-objective particle swarm optimization (MOPSO) algorithm coupled with Monte Carlo simulation (MCS) was employed to obtain the optimal reliable design solutions. Based on the proposed method, an optimal automobile component was given and manufactured with material 22MnB5, and the strength of formed part was evaluated by the tensile test, micro-structure distribution, and micro-Vickers hardness. The numerical results showed that there was a trade-off between the desired reliability level and objective performance because deterministic optimization generated the best cooling capacity while its reliability was the lowest. It is noted that the cooling capacity has a negative effect on reliability. The cooling structural parameters satisfied the requirement because the tensile strength, micro-Vickers hardness, and uniform distribution of martensite of samples are validated.

Correction to: Root tensile strength and root distribution of typical Mediterranean plant species and their contribution to soil shear strength

The original version of this article unfortunately contained a mistake. Figs. 4a and 4c were duplicated. This Figure has now been corrected.

A comparison of mechanical properties and residual stresses of line pipes sized by expansion and compression process

We have investigated and compared the mechanical properties and residual stress distributions in API-X70 pipes sized by expansion and compression processes with different sizing ratios. Various testing methods were applied to examine the target properties (i.e., hardness, yield-to-tensile ratio, drop weight tear test (DWTT) and crack tip opening displacement (CTOD)) which are critical design parameters in line pipe industries. Residual stresses were determined using a conventional hole drilling technique. The results show similar tensile strength and hardness distributions in both processes, whereas an opposite trend in the yield-to-tensile (Y/T) ratio was found where, in compressed pipes, the ratio was lowered. Fracture behaviour showed higher crack arresting and better fracture characteristic in the compression. Compared to the original pipe, residual stresses were considerably reduced in both processes, and in particular there were little or no residual stresses at a compression ratio of 0.3%. The effectiveness of the compression process over the expansion process is elucidated and discussed with respect to mechanical, economic and environmental aspects.

Effect of substrate bias voltage on tensile properties of single crystal silicon microstructure fully coated with plasma CVD diamond-like carbon film

Tensile strength and strength distribution in a microstructure of single crystal silicon (SCS) were improved significantly by coating the surface with a diamond-like carbon (DLC) film. To explore the influence of coating parameters and the mechanism of film fracture, SCS microstructure surfaces (120 × 4 × 5 μm3) were fully coated by plasma enhanced chemical vapor deposition (PECVD) of a DLC at five different bias voltages. After the depositions, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), thermal desorption spectrometry (TDS), surface profilometry, atomic force microscope (AFM) measurement, and nanoindentation methods were used to study the chemical and mechanical properties of the deposited DLC films. Tensile test indicated that the average strength of coated samples was 13.2–29.6% higher than that of the SCS sample, and samples fabricated with a −400 V bias voltage were strongest. The fracture toughness of the DLC film was the dominant factor in the observed tensile strength. Deviations in strength were reduced with increasingly negative bias voltage. The effect of residual stress on the tensile properties is discussed in detail.

Preparation and mechanical properties of controllable orthogonal arrangement of carbon fiber reinforced hydroxyapatite composites

Design of structure and properties of short carbon fibers (CF) reinforced hydroxyapatite (HA) composites is hard to achieve and satisfy performance requirement for weight-bearing bones replacement materials because of agglomeration and uncontrollability of distribution state of short CF. In this study, CF reinforced hydroxyapatite HA (CF/HA) composites with controllable orthogonal arrangement of CF in matrix were first designed and prepared by hot-pressing sintering. Properties of starting monofilament and mixed acid treated monofilament (TCF) were characterized for designing the composites. The results suggest that mixed acid treatment can change surface structure of CF by eliminating some structural defects as well as homogenizing surface structure. Surface roughness of fiber varied from 4.57 nm (CF) to 9.02 nm (TCF). Although tensile strength distribution of the TCF was reduced, average tensile strength of the TCF was reduced more quickly than that of the CF after high temperature treatment. When three-layer CFs was used as reinforcing material, largest bending strength and fracture toughness of 16.57 ± 0.90 MPa and 1.43 ± 0.11 MPa m1/2 respectively were achieved, which increased by 16.77% and 22.22% compared with pure HA, and increased by 50.64% and 25.44% compared with three-layer TCF reinforced HA composites.

Three-dimensional discrete element modelling of three point bending tests: The effect of surface energy on the tensile strength

Understanding the dependence of the strength of agglomerates on material properties, interfacial properties and structure of the agglomerate is critical in many processes involving agglomerates. For example, for manufacturing of pharmaceutical tablets and pellets with dry granulation, understanding the relationship between the ribbon properties and the properties of granules is critical in controlling the granulation behaviour, and the ribbon properties (e.g. tensile strength and density distribution) is determined by the material properties of feed powders, interfacial properties between particles and the process condition, which determine the structure of ribbons. This study aims to investigate the effect of surface energy and porosity on the bending strength of pharmaceutical ribbons, for which three-dimensional discrete element modelling with a cohesive particle model based upon the JKR theory was performed. Simulations were carried out using specimens of various porosities and surface energies. The dependence of the bending strength on the surface energy and the ribbon porosity was examined. It was found that there is a strong correlation between the bending strength with the porosity and the surface energy. In particular, the bending strength is proportional to the surface energy and is an exponential function of the porosity.

Pemanfaatan limbah piston bekas sebagai filler metal aluminium pada pengelasan oxy-acetylene

The abundance of waste piston used so far has not been utilized properly. Users of this piston waste can be used as an oxy-acetylene welder filler. Las oxy-acetylene has been widely used for welding on various types of aluminum product repair, one of which is welding machine block. Machine blocks in their use often suffered damage to the cooling water circulation path and broken crack and broken. Welders and repair shops that repair these damages do not have standardized standards in the use of weld fillers, but they do filler selection based solely on experience including in determining the weld filler. The purpose of this research is to know the effect of piston waste which is used as raw material of weld filler to tensile strength and hardness of welded block result of machine using oxy-acetylene welding. Welding is done by an experienced welder. The welding results are tested for tensile strength and hardness distribution test. The welded joint with the chemical composition of filler which is almost equal to base metal has the highest tensile strength. The tensile strength of the welded joint tension test is in the weld metal region due to defects in the weld metal, especially the porosity defects that are formed during the welding process so that the tensile test loading is concentrated on the defect. While the highest hardness on the weld is in the filler metal with the highest percentage of Si content.

A study of stress concentrations around fiber breaks in unidirectional CF/epoxy composites using double-fiber fragmentation tests

The prediction of tensile strength of unidirectional CF/epoxy composites requires appropriately determining the tensile strength distribution of carbon fibers and calculating the stress concentrations around the fiber breaks. In this study, double-fiber fragmentation tests were performed to investigate the stress concentration factor in adjacent fibers around a broken fiber. Simulation results obtained by considering the additional stress concentration due to the matrix cracks correspond well with the fiber breakage behavior observed in experiments. Furthermore, using an additional stress concentration factor and a bimodal Weibull distribution, which has a narrow strength distribution at the short gauge length, the prediction of tensile strength of the unidirectional CF/epoxy composite exhibited a good agreement with experimental results. These results showed that double-fiber fragmentation tests are a valid means of estimating the stress concentrations around fiber breaks.

Experimental evaluation and modified Weibull characterization of the tensile behavior of tri-component elastic-conductive composite yarn

In order to clarify the effects of the extension rate and gauge length upon the distribution of tensile strength of tri-component elastic-conductive composite yarn (t-ECCY), experimental as well as theoretical studies have been performed in this paper. Influences of the extension rate and gauge length are highlighted. The yarn exhibits an extension-rate strengthening effect, and the higher extension rate results in a higher strength and fracture strain, irrespective of the gauge length considered, and vice versa. Expressed in terms of gauge length, yarn tenacity shows a drop for a longer testing length at all extension rates, based on the weakest-link theory. A modified two-parameter Weibull strength distribution model, taking into account the effects of extension rate and gauge length, can be reasonably used to quantify the degree of variability in tensile strength and to obtain the individual Weibull parameters for practical applications. Different fracture mechanisms of the t-ECCY are demonstrated at lower and higher extension rates. A “cascade-like” break happens at lower extension rates due to inner sliding, weaker interactive transverse force of individual fibers, and sufficient time available for the fiber realignment. Nevertheless, a “chimney-like” break dominates at higher extension rates by virtue of the reduced reorientation of some disordered fibers and intensive instant impact force of the stainless steel filament component along the load direction.

Tensile properties of novel carbon/glass hybrid thermoplastic composite rods

Novel carbon/glass hybrid thermoplastic composite rods consisting of unidirectional PAN-based carbon fiber (T700SC), braids of E-class glass fibers, and thermoplastic epoxy matrix have been developed. Three types of hybrid rods with differing carbon/glass ratios (24K1P, 24K2P, and 24K3P) were fabricated. The cross-sectional morphologies of the hybrid rods were observed using a digital microscope. Volume fractions of carbon fiber, glass fiber, matrix, and void of the hybrid rods were estimated using a specific gravity measurement via ethanol immersion and a thermogravimetric analysis.The tensile properties and fracture behavior of the hybrid rods were investigated. For all hybrid rods, the stress applied to the specimen was nearly linearly proportional to the strain until failure, with a tensile modulus of 65 (24K1P), 87 (24K2P), and 91GPa (24K3P) and tensile strengths of 1.42 (24K1P), 1.80 (24K2P), and 1.84GPa (24K3P). The tensile modulus and strength increased with increasing carbon fiber volume fraction. The Weibull statistical distribution of tensile strength for the hybrid rods was examined. The Weibull modulus of the tensile strengths for the hybrid rods were 23.77 (24K1P), 27.29 (24K2P), and 32.50 (24K3P). The Weibull modulus increased with increasing tensile strength and decreasing void volume fraction of the hybrid rods.

Weibull statistics of tensile strength distribution of gel-cast ultra-oriented film threads of ultra-high-molecular-weight polyethylene

Studies of the potentials of the multi-stage hot-zone drawing technique for enhancing the tensile strength (σ) of ultra-high-molecular-weight polyethylene (UHMWPE) gel-cast highly oriented film threads, the applicability of the Weibull statistics to the σ distribution, and the solvent role in the film thread strength are presented. It is shown that the results of a large number of mechanical measurements for two series of UHMWPE film threads drawn to an ultimate draw ratio (λ) of 120 from xerogels formed from 1.5 % solutions of UHMWPE in decalin or paraffin oil are satisfactorily described by the Weibull model. It is shown that the threads produced are characterised by an average strength σ av = 4.7 GPa and 20 % of the samples have σ = 5.2–6.5 GPa. This is higher than the strength of the commercially available gel-spun oriented UHMWPE fibres of σ = 3.5 GPa. It is found that the solvent nature does not affect the tensile strength of the film threads but exerts a considerable influence on the long-term characteristics.

Effect of process parameters on microstructure and mechanical properties of friction stir-welded Ti–6Al–4V joints

In this work, the microstructure and mechanical behavior of friction stir-welded 2-mm-thick sheets of Ti–6Al–4V alloy were investigated. Specifically, the influence of friction stir welding (FSW) process parameters on microstructure evolution, defect generation, tensile, and hardness properties of the joint were studied. Optical and scanning electron microscopies were used to examine the microstructure and to determine the type and nature of the defects. A progressive change in the microstructure from equiaxed and elongated α grains (base metal) to a very fine lamellar structure with an average grain size of less than 1 μm (in the upper stir zone) was observed and related to FSW parameters. Tensile tests and microhardness measurements were also carried out to assess the mechanical properties. Important variations were observed on tensile strength and hardness distribution as a function of process parameters. The weakest mechanical properties and fracture were found in the heat-affected zone (HAZ) of the as-welded joints. The results were analyzed in terms of the pseudo heat index, and it was determined that tool rotation is the most significant process parameter influencing both the microstructure and mechanical properties of FSWed Ti–6Al–4V joints.

Tensile strength distribution of all-oxide ceramic matrix mini-composites with porous alumina matrix phase

The mechanical behaviour of all-oxide ceramic matrix mini-composites with porous alumina matrix phase was investigated by performing uniaxial tensile tests on specimens with different gauge lengths. The specimens were fabricated from Nextel™ 610 fibres by slurry infiltration and subsequent sintering at 1300°C for 1h.The stress–strain curves of the tested mini-composites revealed that the porous alumina matrix phase accumulates damage with increasing tensile load, but continues to contribute to the mini-composites’ tensile stiffness until ultimate failure occurs. A dependence of the tested mini-composites’ axial tensile strength on gauge length was not observed. The mean stress in the fibres at mini-composite failure was found to decrease with increasing matrix volume fraction, indicating that the cause of ultimate failure of the mini-composites can be attributed to the propagation of matrix cracks.

Strength dependent evaluation method for the wear resistance of multifaceted diamond Berkovich indenter in scratch test

In this work, the superposition principle is introduced to model the dynamic micro tensile strength of diamond crystal in different directions and on any plane. Subsequently, a novel anti-wear strength evaluation factor is proposed to evaluate the wear resistance anisotropy of multifaceted diamond Berkovich indenter, which is directly calculated in terms of the distribution of dynamic micro tensile strength on the pyramid faces. Be consistent with theoretical prediction, the higher is the anti-wear strength evaluation factor on the indenter edge or indenter tip, the better is the wear resistance. Finally, six diamond Berkovich indenters with different crystalline orientations on the pyramid faces are employed to perform the wear tests on the hard sapphire substrates. The results indicate that the experimental observations have a good consistency with the theoretical predictions, which confirms that the newly developed anti-wear strength evaluation factor is effective.

An innovative phosphate-based consolidant for limestone. Part 2: Durability in comparison with ethyl silicate

The durability of a new phosphate consolidant for limestone, based on formation of hydroxyapatite (HAP), was investigated in comparison with ethyl silicate (ES). Untreated, HAP- and ES-treated samples were subjected to repeated wetting–drying, freezing–thawing and salt crystallization cycles. The weathering effects were monitored in terms of alterations in visual appearance, weight, dynamic elastic modulus, tensile strength and pore size distribution. HAP samples performed better than untreated samples and underwent less deterioration in original properties than ES samples. ES samples, subjected to salt crystallization cycles when the treated layer was still hydrophobic, experienced detachment of the consolidated layer.

Laser and pyrolysis removal of fluorinated ethylene propylene thin layers applied on EN AW-5251 aluminium substrates

This work compares laser and pyrolysis removal procedures of the fluorinated ethylene propylene FEP-rich coatings applied on EN AW-5251 H34 aluminium magnesium alloy sheets. The study has been conducted in three successive FEP coating application-removal cycles. Roughness, yield and tensile strength, elongation percentage, hardness, grain size and constituent particles distribution of the processed samples have been analyzed. According to the results, it is concluded that similar mechanical properties has been obtained for both removal technologies, being the laser decoating removal rates lower than those achieved by the pyrolytic procedure. However, the laser decoating process is consolidated as an industrial alternative against the dangerous and harmful (to the environment) pyrolytic extraction systems.

Tensile strength and root distribution of Acacia mangium and Macaranga tanarius at spatial variation(Case study: East-West highway, Malaysia)

Tensile strength and root distribution of Acacia mangium and Macaranga tanarius at spatial variation(Case study: East-West highway, Malaysia)

Effect of different heat treatment conditions on microstructural and mechanical behaviour of AZ63 magnesium alloy

In this study, influence of different heat treatment conditions on microstructure, microhardness, yield strength, ultimate tensile strength, elongation and phase distribution of AZ63 magnesium alloy were discussed. All specimens were taken from as cast commercial AZ63 magnesium alloy. Solution heat treatment was applied at 400 °C for 16 h. After air cooling the specimens to room temperature, the specimens were aged at two different temperatures; 160, 190 °C and five different durations; 1, 3, 6, 9 and 12 h. The effects of heat treatment conditions on the mechanical and microstructural properties of AZ63 magnesium alloy were determined by tensile and microhardness tests, SEM, EDX and XRD analyses, respectively. It was observed that, after the solution treatment, a weak intermetallic phase of Mg17Al12 was dissolved almost totally in the matrix. During ageing, this phase precipitated in the grains and also on the grain boundaries homogeneously depending on the ageing temperatures and times.

Effect of Cristobalite on the Strength of Sintered Fused Silica Above and Below the Cristobalite Transformation

Porous fused silica ceramics which had been partially devitrified to cristobalite were stronger at 350°C in the beta‐cristobalite stability range, but weaker at 25°C after the transformation to alpha‐cristobalite. The tensile strength distribution for different cristobalite fractions are compared for three types of specimens. These were beta‐cristobalite samples which had never been transformed to alpha‐cristobalite; room‐temperature samples with alpha‐cristobalite; and samples at 350°C which had retransformed to beta‐cristobalite after prior transformation to alpha‐cristobalite. The alpha‐cristobalite samples displayed 50%–75% the strength of samples tested on beta and the difference in strength was dependent on cristobalite content. Specimens retransformed to beta‐cristobalite had strength similar to virgin specimens. Microcracking associated with the transformation to alpha‐cristobalite contributes to the strength changes but cannot fully explain the impact of the beta–alpha transformation on strength.

Simulating vegetation controls on hurricane‐induced shallow landslides with a distributed ecohydrological model

AbstractThe spatial distribution of shallow landslides in steep forested mountains is strongly controlled by aboveground and belowground biomass, including the distribution of root cohesion. While remote sensing of aboveground canopy properties is relatively advanced, estimating the spatial distribution of root cohesion at the forest landscape scale remains challenging. We utilize canopy height information estimated using lidar (light detecting and ranging) technology as a tool to produce a spatially distributed root cohesion model for landslide hazard prediction. We characterize spatial patterns of total belowground biomass based on the empirically derived allometric relationship developed from soil pit measurements in the Coweeta Hydrologic Laboratory, North Carolina. The vertical distribution of roots and tensile strength were sampled at soil pits allowing us to directly relate canopy height to root cohesion and use this model within a distributed ecohydrological modeling framework, providing transient estimates of runoff, subsurface flow, soil moisture, and pore pressures. We tested our model in mountainous southern Appalachian catchments that experienced a number of landslides during the 2004 hurricane season. Slope stability estimates under the assumption of spatially uniform root cohesion significantly underpredicted both the total number of landslides and the number of “false positives,” unfailed areas of the landscape that were predicted to fail. When we incorporate spatially distributed root cohesion, the accuracy of the slope stability forecast improves dramatically. With the growing availability of lidar data that can be used to infer belowground information, these methods may provide a wider utility for improving landslide hazard prediction and forecasting.