Key Engineering Materials Vol. 973

Abstract: The forming limit curve (FLC) is commonly used to predict the formability behavior of sheet metal after the forming process. In this research, the forming limit curve generated from the Materials Model was applied to analyze and predict the fracture behavior of the fuel tank workpiece, a motorcycle part made of AA5754-O material, using the deep drawing process simulated by the finite element method. The research involved a comparison with actual cracks that occur in the automotive industry after molding. To determine the mechanical properties of the AA5754-O material for use in the forming limit curve, a specimen with a thickness of 1.5 mm was subjected to a tensile strength test, providing the necessary input for the mechanical properties in the forming limit curve based on the Keeler-Beizer equation. The forming limit curve is a correlation graph between major strain and minor strain. When the FLC is created from the Materials Model, it is utilized in conjunction with deep drawing drag simulation in the PAM-STAMP program to predict the fracture point. The accuracy of the mathematically generated FLC in predicting fracture behavior was verified after the deep drawing process. The study found that the FLC based on the Keeler-Beizer equation can accurately predict the cracking behavior of AA5754-O sheet metal, enabling identification of the fracture location during the deep drawing process. One advantage of creating the FLC from the material models is its compatibility with the same material but with different workpiece shapes, allowing its use in conjunction with molding simulations using various programs. This approach saves costs associated with testing to obtain the FLC.

Abstract: This paper is to study weldability and joining characteristics of dissimilar metal welding between low carbon steel and ferritic stainless steel using ER308L and ER309L filler wires. Weldability and welded joints were evaluated by microstructure analysis and bend test. It was observed that the microstructure of the fusion zone and the bend test of the welded joint were significantly affected by welding parameters and filler wire. A welded joint prepared with high heat input using the ER309L filler wire exhibited a significant delta ferrite and austenite microstructure. In contrast, when employing the ER308L filler wire with a high intensity welding current, martensite, and carbide formed at the fusion zone. The bend property was acceptable for all the specimens, and there was no evidence of solidification cracking.

Abstract: In this study, the controllability of the spring performance of complex sheet spring shapes was investigated to develop complex sheet spring shapes that are based on origami engineering, with the aim of integrating laser hardening formation with origami engineering. The number of forms generated during the same development was predicted from an origami engineering perspective, and two forms that agreed with the experimental results were generated. Consequently, the rigid-body origami simulation showed that the deformation behavior differs from that of the measured values, which is considered to be in accordance with elastic-body origami. Moreover, springs with arbitrary performances could be produced by varying the processing time and form.

Abstract: Deep drawing process is a common sheet metal forming technique in motor vehicle manufacturing. There are three primary defects that could be occur in deep-drawn parts: tearing, wrinkling, and thinning. When the thinning is difficulty detected by visual inspection. As a result, this study aims to address the thinning issue in a fuel tank part made from an aluminum alloy sheet AA5754-O 1.5 mm thick under cold working deep drawing process, while the manufacturer's desired upper limit for thinning is 20%. Two influential parameters viz. blank holder force and initial size of blank, were investigated and optimized by using Finite Element Analysis (FEA) through PAM-STAMP simulation software with the validated material model was based on Hill’s 1948 anisotropic yield criterion with Swift hardening law. The mechanical parameters in the mentioned model were derived from the results of uniaxial tensile tests. In conclusion, both the hydraulic cushion's blank holder pressure and the initial size of the blank were found to influence the thinning of the part, either individually or in combination. Despite optimizing both parameters, they were unable to consistently achieve the desired limit.

Abstract: To address global environmental challenges and mitigate bamboo-related ecological damage, this study focuses on the development of self-adhesive molded products utilizing solely bamboo fibers and powder obtained through machining center extraction. However, the mechanical properties of these molded products remain inadequate. This study utilizes Scanning Electron Microscope (SEM) and Fourier transform infrared spectrometer (FTIR) analyses to explore the disparities associated with chip size as raw materials for molded products. Bamboo fiber, characterized by its substantial cellulose content and high strength, is contrasted with bamboo powder, which contains significant amounts of lignin and exhibits potential adhesive properties. Building upon these findings, the powder was added to the conventional fiber alone, with results demonstrating that a predetermined ratio (20%) of the powder yields optimal mechanical properties. Moreover, employing a parameter representing the degree of lignin flow utilized in previous molding studies, the study establishes the optimum molding conditions (PD'=1.031) to maximize tensile strength (37.8 MPa) when incorporating a 20% powder mixture.

Abstract: A process when different materials are combined to produce a product with multiple layers is called co-extrusion. During this process, polymers are melted in separate machines and then extrudate from different die channels. Once these channels converge, the polymers meet and flow through a single channel. The surface where the two fluids face is called “interface”. It is crucial to maintain the interface's uniformity and stability in order to achieve the desired multi-layered structure. Most of the issues in co-extrusion are related to issues that can be classified into two categories such as polymer encapsulation/interfacial distortion and die swell. To solve these problems, designers focus on improving the interface's stability. This paper examines effects of cross-section modification of the two-channel feedblock on the interface location and velocity and pressure distributions of the flow. The ANSYS software was used to simulate the co-extrusion of polymers, LLDPE and HDPE, in two-channel feedblock with rectangular, circular, and straight slot cross-sections. The results show that sharp corners increase the thickness of dead zones, while rounding them decreases the thickness. Additionally, stadium-shaped (or straight-slot) cross-section channels can move the flow with a higher maximum velocity and thinner boundary layer combining the results of rectangular and circular feedblocks.

Abstract: When using the coat hanger die method for co-extrusion, the biggest challenges often involve maintaining the uniformity of the velocity distribution at the outlet of the die and ensuring the stability of the interface plane. This paper investigates the effect of different cross-section of feed channels connected to the coat hanger die on the velocity and pressure distribution of the flow at different parts of the die. Co-extrusion of LLDPE (Linear Low Density Polyethylene) and HDPE (High Density Polyethylene) polymers is simulated using ANSYS software 2020 R2 for coat hanger die design with rectangular and circular cross-sections inlet geometry; the results are compared for Carreau-Yasuda model to observe the result differences between rectangular and circular coextrusion channels connected to coat hanger die. Our results showed that rectangular cross-section feedblock generated higher values for pressure in comparison with the pressure generated by the circular cross-section feedblock. The maximum velocity generated in the circular feedblock is lower than that generated in the rectangular one, nevertheless there is more uniformity in velocity distribution in circular than rectangular cross-section.

Abstract: This research paper aims to investigate the significance of considering the humidity factor during material selection in plastic product design. Humidity is a crucial environmental parameter that can profoundly influence the properties and performance of plastic materials. To ensure the long-term performance and dependability of plastic products, it is essential to comprehend and take into consideration the impacts of moisture on plastics. Humidity plays a fundamental role in the degradation and functional changes of plastic materials. Moisture absorption can lead to reduced mechanical strength and accelerated degradation processes. The selection of appropriate materials that can withstand humid conditions becomes paramount in product design. For this reason it is important to evaluate the moisture absorption properties of plastic materials. Different polymers exhibit varying degrees of moisture diffusion rates that directly affect their performance in humid environments. Evaluation of moisture measurement results allows designers to make informed decisions during material selection. For this reason, we designed an experiment to investigate which material retains less moisture. In our research, we determined 2 different experimental groups. The first of these groups (type A) was kept under normal conditions by adding glass fiber additive at different rates to the PA66 material, and each product with 3 different additives was tested for moisture for 10 days and the results were recorded. In the second experimental group, type B, the products produced with the same material and additives at the same rate were kept in water for 24 hours, then they were removed from the water and moisture tests were performed. It is aimed to make material selection by interpreting the test results and thus to facilitate the making of designs suitable for use.