Tensile Fracture Resistance Research Articles

Fracture toughness of 3D printed denture teeth.

Advances in digital dentistry lead to use of three-dimensional (3D) printed resin denture teeth. Fracture toughness of these teeth must be assessed. This study aimed to compare the chipping and indirect tensile fracture resistance of denture teeth fabricated by 3D printing technique with traditionally fabricated resin denture teeth. Four groups (Gr) were made (n= 50/group): Gr-1 3D printed denture teeth (denture teeth; Formlabs Inc., Somerville, MA, USA), Gr-2 SR-Orthosit-PE (Ivoclar Vivadent AG), Gr-3 Portrait IPN (Dentsply Sirona), Gr-4 Pala Premium 8 (Heraeus Kulzer GmbH). Stereolithography 3D printing was used to create the methacrylate-based photopolymerized resin teeth models and remaining group teeth were collected commercially. A 1 mm/min chipping and indirect tensile fracture speed tests were carried out till fracture occurred. The data so obtained were statistically analysed using one-way analysis of variance with Tukey's honestly significant difference multiple comparisons test (p< 0.05). At the end of the test, the fractured areas of the specimens were evaluated by the chief researcher to assess the fracture pattern of the teeth. The indirect tensile fracture values of the 3D printed teeth were more than that of Pala Premium-8 and SR-Orthosit-PE but it was lower than that of Portrait IPN teeth. In chipping test, buccal chipping of the loaded cusp was seen in 3D printed resin without distortion and in indirect tensile test in 3D printed resin teeth, line of fracture emerges near the loading point propagates from the inner incline of both cusps and extends cervically, unlike in other groups where first deformation occurs then fracture. Prosthetic teeth fabricated by the 3D printing technique using printable resin material provide adequate fracture resistance as denture teeth.

Controlling Rice Leaf Breaking Force by Temperature and Moisture Content to Reduce Breakage

Leaf fragments and grain mixture produced by rice threshing with a combine harvester seriously affects the subsequent grain cleaning efficiency. In this paper, rice leaf breaking force was tested at different temperatures and moisture contents to analyze the influence of temperature on the tensile properties of rice leaves. The overlapping regions of rice leaf breaking force and grain separation force at different temperatures were obtained. Based on the rice leaf breaking force, the effect of the temperature change on rice leaf with different moisture content was analyzed. The results showed that tensile strength of rice leaf decreased first, then increased and finally decreased from rice sheath to the top. The tensile breaking force of the leaf sheath was about 75 N (N is Newton, 1 N = 1 kg·m/s²). The tensile fracture resistance of rice leaf was shown to weaken with the increase of temperature. The influence of the moisture content on the mechanical properties of rice leaf during the process of temperature change was small. At 30 to 35 °C, the blade was the strongest tensile fracture resistance, which was the lowest probability of fracture under the same stress condition. At this time, the rice grain separation force has the least coincidence with the rice leaf resistance to breakage. According to the breaking force of different blade layers, the number of blade layers has a significant linear relationship with its tensile limit. Therefore, the overall fracture resistance of the multilayer blade can be improved by controlling the temperature and moisture content.

3D Printing of Resin Material for Denture Artificial Teeth: Chipping and Indirect Tensile Fracture Resistance.

3D printing of denture artificial teeth with resin materials is worthy of study in a novel way. This study evaluated chipping and indirect tensile fracture resistance of 3D printing resin material (Dentca 3D printing denture teeth resin) compared with conventionally prefabricated resin denture teeth (Premium-8, Surpass, SR-Orthosit-PE, and Preference). One hundred tooth specimens were prepared for testing. The 3D printed tooth specimens were printed at a 50 µm layer thickness with methacrylate-based photopolymerized resin by stereolithography 3D printing. Chipping and indirect tensile fracture tests were conducted at a speed of 1 mm/min until fracture. The indirect tensile fracture loads of the 3D printed resin teeth were higher than those of Premium-8, Surpass, and SR-Orthosit-PE, and lower than those of Preference teeth. Regarding chipping resistance, the 3D printed resin teeth were not different from Surpass and SR-Orthosit-PE, and were lower than Premium-8 and Preference teeth. The 3D printed resin teeth exhibited vertical fracture of the loaded cusp without deformation in chipping. The 3D printed resin teeth showed simultaneous fracture of two cusps in indirect tensile fracture, unlike other teeth. The results of this study suggest that 3D printing technology using resin materials provides adequate fracture resistance for denture artificial tooth use.

The Strain Capacity of the Girth Weld Joint Cracked at “Near-seam Zone” in Tensile Test

The specimens of girth weld joint of Φ813mm×14.7 mm pipeline cracked at “near-seam zone” in tensile test. It was considered unacceptable for strain-based design pipelines in some current standards. The girth weld joint for X70 pipelines with “near-seam zone” crack were researched by CWP test and single-edge notch test (SENT). The high strain capacity is demonstrated by resistance curve tangency approach and CWP test results. The results imply the considerable tensile fracture resistance and consequently strain capacity when the strength overmatch.

Tensile fracture resistance mechanisms in brittle polycrystals: An ultrasonics and in situ microscopy investigation

A zone of distributed microcracking is often suggested to accompany tensile macrocrack propagation in rocks and ceramics. The microcracking is said to be largely responsible for (1) high values of fracture energy, (2) increasing resistance to fracture with crack extension and (3) the dependence of fracture mechanics data on the experimental setup. In the present paper, the material breakdown processes in imperfectly elastic Westerly granite are investigated using ultrasonic wave probing and in situ microscopy during mode I fracture experiments. These observations are compared with an in situ reflection/transmission microscopy investigation of mode I fracture in a near‐ideal elastic polycrystalline alumina (Al2O3). As defined by the spatial distribution of longitudinal and surface wave attenuation in wedge‐loaded double‐cantilever beam specimens of Westerly granite, the fracture process zone is elongate in the direction of fracture propagation (15–40 mm long by 1–2 grain dimensions wide; grain size 0.75 mm). As revealed by in situ reflection microscopy, the ultrasonic wave energy is partially transmitted through the developing fracture surfaces via two sources of crack interface traction: (1) remnant islands of unfractured material left behind the advancing fracture front and (2) geometrical interlocking of the microstructurally rough fracture surfaces. A similar zone of crack flank tractions is found in the alumina (greater than 2000 μm long; grain size 20–100 μm). No evidence of a diffuse kidney‐shaped cloud of microcracking distributed ahead of the main fracture tip (predicted by many fracture models) was found in either material. Instead, interface‐localized microcracking was observed to operate at positions where the tractions, or restraining forces, are transmitted across the nascent fracture surfaces. Crack flank tractions shield the main crack tip from high levels of stress and are relieved by friction‐induced microcracking and microcrack rupture of intact‐material bridges. As a consequence of the crack history dependence of the crack tip shielding, it is proposed that, even under small‐scale inelastic deformation conditions appropriate to linear elastic fracture mechanics, neither R‐curve behavior nor applied‐KI/subcritical crack velocity relationships are intrinsic properties of these and similar materials.

Resistance of bony tissue to tensile fracture

The tensile fracture resistance of compact bony tissue is considered. The relation between specific strain energy and stress level is established. A strength criterion characterizing the degree of deformation is proposed on the basis of a model, according to which compact bony tissue may be regarded as a composite material. The mode of variation of the proposed resistance parameter over the various zones of the cross section of the diaphysis of a human tibia has been experimentally established.