Specimen Size Research Articles

Sedimentation-affected engineering performances and microstructures of a hybrid Portland-sulfate aluminate cement grout cast in long tubes

Material sedimentation may have non-negligible impacts on engineering properties of flowable cement grouts, and this issue cannot be addressed by in-lab tests on small size specimens. Herein, sedimentation tests were conducted to a high-strength hybrid Portland-sulfate aluminate cement (P-SAC) grout cast in 6-m-long tubes. Compressive strength and density of the P-SAC specimens at different depths were measured, and microstructures were assessed by X-ray computed tomography (XCT), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Results showed that the hybrid P-SAC grout possessed the superior indices of flowability, expansion and compressive strength. The increasing rates of density and compressive strength to depth were 9.3 kg/m4 and 0.5 MPa/m, respectively. The shallow sites possessed a porous structure with 14.5 % more big pores (>1 mm). The pore structure followed fractal patterns, and the fractal dimensions increased slightly with depth. Our findings not only deepen the understandings in slurry sedimentation and the consequences of engineering properties, but also narrow the knowledge gaps between in-lab tests and in-situ applications for grouting construction.

Effects of burnt sawdust ashes from timber species on the strength properties of laterite-interlocking blocks

The most basic problem facing man is shelter, apart from food. This problem is acute in Ghana and other developing countries due mainly to the high growth rate of the population, inflation, unemployment and poor economic resources. Today in Ghana both middle and low income earners can hardly afford their own houses. From one point of view one can see that some of the materials used in building are of good quality and can last. The study aimed to partially replace ordinary Portland cement (oPc) with burnt sawdust ash (BSDA) from different timber species (Wawa, Mansonia, Teak, Odum, Ceiba, Essah and Mahogany) in making interlocking laterite blocks by replacing 0–30 wt %. Mix proportion was 1:8 (cement + BSDA: laterite) with a 0.60 water-to-cement ratio. 528 specimens of size 185 mm × 220 mm × 120 mm were produced and cured at normal temperature and humidity under shady and sunny conditions for 7, 14, 21 and 28 days. Compressive and tensile strengths were subsequently evaluated. However, an initial strength increase was observed with curing time for specific wood species (Wawa, Mansonia, Teak, Odum, Essah, Ceiba, and Mahogany). Notably,Wawa, Mansonia and Odum ash exhibited superior strength performance at 10–20% replacement levels, potentially satisfying relevant standards for load-bearing wall construction. This research suggests that up to 10% replacement with Wawa, Mansonia or Odum BSDA presents a promising eco-friendly approach for partially substituting oPc in LIB production.

Tensile Constitutive Model of Engineered Cementitious Composites Reinforced by High-Strength Steel Wire Mesh.

The presentation of a constitutive model could help researchers to predict the mechanical behavior of a material, which also contributes to the further generalization of the material. This paper is to explore the tensile constitutive model of engineered cementitious composites (ECCs) reinforced by high-strength steel wire mesh based on experiments and numerical simulations. DIANA was used to simulate the tensile process of the specimens, and experiments were carried out to validate the numerical model. The effect of the ECCs' tensile strength, reinforcement ratio and specimen size were considered during the specimen design process. The results showed that most of the errors of the simulated values compared to the experimental results were within 5%, which proved that the numerical model was quite accurate. The proposed constitutive model revealed the different roles played by ECCs and high-strength steel wires at different stress stages, and the calculation results were in high agreement with the simulation results, indicating the effectiveness of the constitutive model. The study in this paper could provide an important reference for the popularization and application of ECCs reinforced by high-strength steel wire mesh.

The Efficacy of Aloe vera Against Enterococcus faecalis as an Intracanal Medicament: A Systematic Review and Meta-Analysis.

Calcium hydroxide (CaOH) is commonly used as an intracanal medicament due to its antimicrobial properties; its antibacterial property depends on the release of hydroxyl ions. By analyzing experimental in vitro studies related to the research question, many studies carried out bacterial inoculation on extracted human teeth or laboratory Petri dishes.This review article seeks to assess the antimicrobial efficacy of Aloe vera (AV) againstEnterococcus faecalisin comparison to CaOH as an intracanal medicament.After being retrieved from databases such as PubMed, Scopus, the Cochrane Library, and EBSCOhost, publications from 2013 to 2024 were screened against our inclusion criteria. As a result, seven papers were included in the systematic review and four in the meta-analysis. Using a meta-analysis (Stata software version 16.0, StataCorp LLC, College Station, TX) to compare colony-forming units (CFUs) formed by CaOHand AV, forest plots were created to record the specimen size, mean, and standard deviation value of the outcome in CFU, at 95% confidence intervals. AV exhibits bactericidal qualities that are equal to or comparable to those of CaOH. AV displayed a nonsignificantly reduced CFU count than CaOH in a meta-analysis (p > 0.05). In summary, AV exhibits antibacterial/antimicrobial capabilities against E. faecalis that are equal to or comparable to CaOH.

Translaminar fracture toughness characterisation for a glass fibre/polyamide 6 laminated composite by a novel approach based on fictitious material concept

This paper proposes a novel approach for the characterisation of the material fracture toughness associated with translaminar tensile failure, consisting in the application of the Fictitious Material Concept (FMC) by using the testing configuration of the Modified Two Parameter Model (MTPM). The main advantage of such an approach is to avoid the use of nonlinear fracture mechanics for material fracture toughness characterisation. The novel approach is applied to compute the translaminar fracture toughness of a unidirectional glass fibre (GF)/polyamide 6 (PA6) laminated composite. Moreover, the experimental campaign carried out is numerically simulated by means of a micromechanical finite element model, and the fracture toughness is computed by employing two different approaches, that is, the novel one and the MTPM. The present study proves, for the first time, that the Fictitious Material Concept can be applied by considering both experimental and numerical structural responses since it provides, in both cases, quite satisfactory accuracy in term of laminated composite fracture toughness. Therefore, the great advantage is that, when a validated numerical model is available, experimental campaigns may be avoided, saving time and money. Moreover, it is proved that the FMC can be used to investigate specimen size effect on fracture toughness.

Correction method and verification of radial inertia and friction effects under a unified deformation framework in SHPB experiments on soft materials

During the split Hopkinson pressure bar (SHPB) experiments, significant measurement errors can arise due to severe radial inertia and friction effects. Previous studies have developed various correction methods for these two effects. However, these methods have problems such as over-reliance on the volume invariance assumption of the specimen and inconsistent assumptions on the deformation patterns of the two effects, which limit their universality and effectiveness. Therefore, this paper integrates the radial inertia effect and friction effect in a unified deformation framework through reasonable assumptions, and proposes a method to correct the specimen from a complex stress state to a uniaxial stress state. SHPB numerical simulation experiments demonstrate that this method effectively eliminates the combined effects of radial inertia and friction on measurement results for both elastic and viscoelastic materials, including the size effect associated with these two factors. Additionally, the paper presents a scheme to determine the friction coefficient using the size effect of the specimens when the friction coefficient between the specimen and the bar is unknown. Finally, the method was applied to correct the stresses measured in SHPB experiments on silicone rubber of different diameters. It successfully eliminated discrepancies in the stress-strain relationships between specimens of various sizes and determined a friction coefficient that fell within a reasonable range.

Experimental evaluation of the synergistic effect of calcium precursor dosage and bacterial strain interactions on the biogenic healing potential of self-healing cement mortar

This study investigates the microbially induced calcium carbonate precipitation (MICP) in repair mortar, focusing on the impact of calcium precursor dosage and bacterial strain selection. C6H10CaO6·xH2O and (CH3COO)2Ca·xH2O were used as calcium precursors at dosages of 0.1, 0.25, and 0.4 M with Bacillus subtilis VEB4, Priestia megaterium TSB16, and Halobacillus halophilus MCC2188 microbes. Quantitative assessment of precipitate and optimization of precursor dosages were conducted before making mortar cube specimens of size 70.6 × 70.6 × 70.6 mm with bacterial spores and nutrients immobilized in Modified Expanded Perlite. Cracked cube specimens underwent automated wet-dry cycles of 12 h daily for 60 days to induce healing. Comparative analysis of biomortar specimens showed P. megaterium as the most effective in compressive strength recovery (up to 89.33%) and crack healing with a maximum healed crack width of 0.64 mm, followed by B. subtilis with significant CSR improvements. H. halophilus, less efficient in non-saline conditions, healed cracks up to 0.48 mm. Calcium lactate was considered the better calcium source choice for B. subtilis and P. megaterium strains, whereas calcium acetate improved MICP by H. halophilus. Microstructural analysis of healed precipitates collected from cracked cubes identified distinct morphology of MICP and the presence of polymorphs viz, calcite, aragonite, and vaterite. Tailored selection and dosage of calcium precursors for each strain significantly enhanced MICP and improved the quality of healing products in cracks, advancing the understanding of self-healing construction biomaterials.

A Custom-Developed Device for Testing Tensile Strength and Elasticity of Vascular and Intestinal Tissue Samples for Anastomosis Regeneration Research.

Optimizing the regeneration process of surgically created anastomoses (blood vessels, intestines, nerves) is an important topic in surgical research. One of the most interesting parameter groups is related to the biomechanical properties of the anastomoses. Depending on the regeneration process and its influencing factors, tensile strength and other biomechanical features may change during the healing process. Related to the optimal specimen size, the range and accuracy of measurements, and applicability, we have developed a custom-tailored microcontroller-based device. In this paper, we describe the hardware and software configuration of the latest version of the device, including experiences and comparative measurements of tensile strength and elasticity of artificial materials and biopreparate tissue samples. The machine we developed was made up of easily obtainable parts and can be easily reproduced on a low budget. The basic device can apply a force of up to 40 newtons, and can grasp a 0.05-1 cm wide, 0.05-1 cm thick tissue. The length of the test piece on the rail should be between 0.3 and 5 cm. Low production cost, ease of use, and detailed data recording make it a useful tool for experimental surgical research.

Size effect on tensile bonding strength between new and old concrete

The interface between new and old concrete plays a significant role in reinforced concrete engineering due to its size effect and weak strength. To investigate the size effect of tensile strength in new-to-old concrete, splitting tensile tests and computed tomography (CT) scans on composite specimens were conducted. Specimen size, interface roughness, volume fraction of polyvinyl alcohol fiber and adhesive were considered. The tensile bonding strength initially increases and then decreases with interface roughness and fiber content, while size effect on the strength shows a downward trend before rising. The adhesive notably enhances the tensile bonding strength and weakens its size effect. The interface roughness, polyvinyl alcohol fibers and interface agents influence the size effect by modifying the bonding area, specimen uniformity, and characteristic structure of the interface region. At an interface roughness of 5.5 mm and a polyvinyl alcohol fiber content of 0.5 %, the maximum strength was achieved and the maximum attenuation of size effect occurred. The size effect laws of tensile bonding performance were presented based on the Weibull statistical theory, Bažant energy theory and Carpinteri multi-fractal theory. The experimental values exhibit good consistency with the predictions from the size effect models.

Influence of dimensional deviation and thickness non-uniformity on the small-size specimen tensile results of CLF-1 steel

Tensile testing of small-size specimens has been widely used to evaluate the influence of neutron irradiation on the mechanical properties for structural materials of fusion reactors. In recent years, researchers have been trying to standardize small-size specimen tensile test method. In the present paper, we have investigated the influence of dimensional deviation and thickness non-uniformity on the tensile results of small-size specimen by both experiments and finite element simulations, based on one of the candidate structural materials of fusion reactor, i.e. CLF-1 steel. It was found that under the conditions of small grain size, small metallurgical defect size and suitable specimen preparation, the tensile results of SS-J3 specimen could be close to the results of large-size specimen. Slightly higher yield and ultimate strengths for small specimens may be caused by the surface treatment of the wheel grinding. The repeatability of ultimate strength was better than that of yield strength, and the repeatability of elongation was worse than that of strength. For tensile tests on eight SS-J3 specimens, the maximum difference in total elongation was about 3 %. With ±0.1 mm deviation of thickness and parallel width, the maximum variation in total elongation was about 1.8 %. The ductility properties were sensitive to specimen's thickness non-uniformity, the measured uniform and total elongations would obviously decrease even with 0.01 mm thickness non-uniformity.

Evaluating the impact of specimen and punch sizes on the tensile strength of UHPC through double punch testing

Many studies have shown that direct tensile tests are fraught with numerous challenges. The Double Punch Test (DPT) is considered a more reliable alternative for evaluating tensile properties among the indirect tensile methods. While DPT is efficient and reliable, its size effect should not be overlooked. Previous studies on DPT size effects have primarily focused on specimen size, with little discussion on the impact of punch size variations. Additionally, with the evolution of construction materials, the applicability of the generalized DPT formula to new materials, such as Ultra-High-Performance Concrete (UHPC), with its exceptional strength, toughness, durability, and crack resistance, needs to be evaluated. This study conducts experimental research on UHPC, focusing on the relationship between specimen and punch sizes and their impact on tensile strength measurements. By designing experiments with 12 different specimen sizes and punch ratios, we explore the differences between actual experimental results and simplified formula calculations. Bažant's theoretical methods are also applied to analyze the size effects of specimen and punch dimensions on DPT. The results indicate that, with appropriate specimen size and punch ratio, DPT can provide tensile strength measurements closer to those of Direct Tensile Tests (DTT). It was also found that tensile strength, strain, and toughness decrease with increasing specimen size. When the ratio of UHPC specimen to punch size (d/D) is 1/3, the results align well with the predictions of the simplified formula. This indicates that the optimal punch ratio is not fixed for different specimen sizes. These findings offer valuable references for designing related experiments and improving quality control and structural performance in various engineering fields.

Specimen size effect on compressive strength of 3D printed concrete containing coarse aggregate with varying water to binder ratios

This study aims to investigate the specimen size effect of compressive strength in 3D printed concrete containing coarse aggregate (3DPCA). Firstly, we compare the specimen size effect of compressive strength in mold-cast concrete (CC) and 3DPCA. Through X-CT scans and image analysis, the underlying mechanisms of this specimen size effect in 3DPCA are revealed. The results indicate that 3DPCA exhibits a less pronounced specimen size effect on compressive strength when loaded along the Z direction compared to CC, due to the presence of interlayer weak zones that mitigate the influence of size variations. Specifically, when the water-binder ratio varies between 0.3 and 0.5, the size coefficient of printed sample is reduced by 0.01–0.07 compared to cast sample. Similarly, variations in coarse aggregate content result in a size coefficient for printed sample that is 0.01–0.05 lower than cast sample. Higher porosity increases the specimen size effect of 3DPCA, but good printing quality can mitigate this influence. A modified Weibull model integrating water-binder ratio and coarse aggregate content was proposed, providing precise predictions of the specimen size effect on 3DPCA's compressive strength, with a correlation coefficient exceeding 93 %.

Consistency in the Assessment of Dried Blood Spot Specimen Size and Quality in U.K. Newborn Screening Laboratories.

In 2015, U.K. newborn screening (NBS) laboratory guidelines were introduced to standardize dried blood spot (DBS) specimen quality acceptance and specify a minimum acceptable DBS diameter of ≥7 mm. The UK 'acceptable' avoidable repeat rate (AVRR) is ≤2%. To assess inter-laboratory variability in specimen acceptance/rejection, two sets of colored scanned images (n = 40/set) of both good and poor-quality DBS specimens were distributed to all 16 U.K. NBS laboratories for evaluation as part of an external quality assurance (EQA) assessment. The mean (range) number of specimens rejected in the first EQA distribution was 7 (1-16) and in the second EQA distribution was 7 (0-16), demonstrating that adherence to the 2015 guidelines was highly variable. A new minimum standard for DBS size of ≥8 mm (to enable a minimum of six sub-punches from two DBS) was discussed. NBS laboratories undertook a prospective audit and demonstrated that using ≥8 mm as the minimum acceptable DBS diameter would increase the AVRR from 2.1% (range 0.55% to 5.5%) to 7.8% (range 0.55% to 22.7%). A significant inverse association between the number of specimens rejected in the DBS EQA distributions and the predicted AVVR (using ≥8 mm minimum standard) was observed (r = -0.734, p = 0.003). Before implementing more stringent standards, the impact of a standard operating procedure (SOP) designed to enable a standardized approach of visual assessment and using the existing ≥7 mm diameter (to enable a minimum of four sub-punches from two DBS) as the minimum standard was assessed in a retrospective audit. Implementation of the SOP and using the ≥7 mm DBS diameter would increase the AVRR from 2.3% (range 0.63% to 5.3%) to 6.5% (range 4.3% to 20.9%). The results demonstrate that there is inconsistency in applying the acceptance/rejection criteria, and that a low AVVR is not an indication of good-quality specimens being received into laboratories. Further work is underway to introduce and maintain standards without increasing the AVRR to unacceptable levels.

Impact of specimen size on mixed mode I and II fracture behavior of asphalt mixture using MMTS criterion

This study investigates how the diameter of specimens impacts the cracking behavior of asphalt mixtures. Testing was conducted on SCB specimens with diameters of 64, 86, and 150 mm under different fracture modes and temperatures. Fracture toughness and fracture energy, crucial fracture parameters, were determined for the tested specimens. The findings revealed that an increase in Me (mode mixity) values led to a decrease in fracture toughness but an increase in fracture energy. By considering all specimen sizes and test temperatures, the fracture toughness for mixed mode I/II and pure mode II was, on average, 13 % and 29 % lower than that for pure mode I loading, respectively. Conversely, the fracture energy for mixed mode I/II and pure mode II was, on average, 19 % and 38 % higher than that for pure mode I loading, respectively. Larger specimens exhibited enhancements in both fracture toughness and fracture energy. Considering all loading modes and test temperatures, the fracture toughness for specimen diameters of 86 mm and 150 mm was, on average, 9 % and 26 % higher than that for a diameter of 64 mm, respectively. The corresponding improvements in fracture energy were 8 % and 14 %, respectively. Additionally, it was observed that fracture toughness increased with decreasing temperature until −20 °C, after which it declined. On the other hand, fracture energy rose with increasing test temperature for all specimen sizes and mode mixities, with a notable increase at 10 °C due to the brittle nature of asphalt concrete. Moreover, the size of the fracture zone (rc) was influenced by temperature and specimen size (R), with larger R resulting in an increase in rc. However, a decrease in temperature initially caused a slight decrease in rc followed by an increase. The study concluded that the MMTS (modified maximum tangential stress) criterion effectively predicted the fracture behavior of SCB specimens across various sizes and loading modes, providing accurate estimations for asphalt mixture fracture behavior. By considering all loading modes and test temperatures, the average error values were 5.9 %, 6.2 %, and 6.5 % for specimen diameters of 64 mm, 86 mm, and 150 mm, respectively.

Low constraint fracture toughness testing for master curve reference temperature determination using 10 mm-thick SE(B) and SE(T) specimens

The constraint correction methodology for defect assessment is not widely applied in fitness-for-service codes in the nuclear industry and there are a limited number of testing standards to account for low-constraint testing. In this work, fracture toughness testing was performed with two different types of alloy steels. SE(B), C(T), and SE(T) specimen configurations were used, along with varying a/W ratios and specimen sizes, allowing for varying levels of constraint. New quality assurance measures related to selection of testing temperature, crack front straightness, and compliance for low constraint specimens are suggested. The results show that the SE(B) specimens are sensitive to CMOD measurement point location. Future work should be focused on improving and validating the instrumentation and analysis practices for low constraint specimens. Yet, the obtained SE(T) T0 values follow models predicting the effect of constraint loss developed using larger specimens. The work impacts the development of quality criteria for future low constraint testing standards.

A new strain-based approach to investigate the size and geometry effects on fracture resistance of rocks

In this paper, a new strain-based criterion is suggested for assessing the effects of size and geometry of specimen on the fracture resistance of rocks under mixed-mode (I/II) loading. The new approach named the modified maximum tangential strain (MMTSN) criterion is based on the classical maximum tangential strain (MTSN) criterion, in which the first non-singular term (T) of Williams series expansion is considered in addition to the singular terms (K). Furthermore, to provide more coherence, the critical distance (rc) from the crack tip is defined according to a new strain-based failure model. Unlike similar strain-based fracture models available in the literature, the critical distance rc in the MMTSN criterion is assumed to be size-dependent and a semi-empirical formulation is utilized for describing this size-dependency. To assess the ability of MMTSN for considering the size and geometry effects, the experimental data existing in the literature for a number of cracked Brazilian disk (CBD) and semi-circular bend (SCB) specimens manufactured from Guiting limestone are taken into account. It is demonstrated that the MMTSN criterion can predict the experimental data very well by taking into consideration the size and geometry effects without needing to calculate the other higher order terms.

Assessment of fracture criteria for cracking behavior of asphalt concrete using various SCB specimen sizes

AbstractIn this research, five fracture criteria (maximum tangential stress (MTS), generalized maximum tangential stress (GMTS), minimum strain energy density (SED), generalized minimum strain energy density (GSED), and modified maximum tangential stress (MMTS)) were evaluated for asphalt concrete using fracture data from tests conducted under various loading modes and conditions. Tests were performed on semi‐circular bend (SCB) specimens of various sizes. Based on the results, the MTS criterion tends to overestimate fractures, while the GMTS criterion exhibits more precise predictions. The SED and GSED criteria inaccurately predict fractures, especially under certain loading conditions. The MMTS criterion shows superior predictive capability for asphalt concrete fractures. Specimen size influences fracture resistance, with larger specimens exhibiting higher fracture values. Overall, the MMTS criterion closely mirrors the crack growth behavior of asphalt concrete, highlighting its precision in predicting fracture results. The errors between the predictions of the fracture criteria MTS, GMTS, SED, GSED, and MMTS, and the experimental results ranged from 0% to 42.8%, 0% to 22.5%, 0% to 52.7%, 0% to 42.4%, and 0% to 14.5%, respectively.

The length of fracture process zone deciphers variations of rock tensile strength

Tensile strength is one of the most critical design factors in many rock engineering projects. However, despite many available testing techniques, an accurate estimation of the true tensile strength of quasi-brittle rock-like materials is yet a controversial problem since it can vary by the shape and size of a test specimen, the adopted test method, and applied loading conditions. Different studies have tried to address this issue by providing (mainly empirical) laws for determining variations of rock tensile strength as a function of a particular test parameter such as specimen size. In this study, however, a new general approach is presented that can decipher the tensile strength variations of rock under various testing conditions. Using coupled Finite Fracture Mechanics (FFM), it is first proved that the length of the Fracture Process Zone (FPZ) can be determined with accuracy and ease using the energy criterion of coupled FFM. Then, the length of FPZ is used in the stress criterion of coupled FFM to determine rock tensile strength. The failure stress of a material is then proved to be mainly a function of the FPZ length following a power law originated from the Linear Elastic Fracture Mechanics (LEFM). The results assist in deciphering variations of rock tensile strength related to the sample size and test method.

Tensile testing of S690QL1 HSS welded joint heterogeneous zones using small scale specimens and indentation methods

Abstract The welded joints are structures with significant heterogeneity, indicated by their fundamental segmentation into base metal (BM), heat affected zone (HAZ), and weld metal (WM). The heat affected zone, having width in millimeter scale for fusion welding processes, is further segmented into several characteristic regions, having differences in grain structure and size. The microstructural heterogeneity results in significant differences in mechanical properties of individual welded joint zones. Mechanical testing of such small material volumes is inconvenient, or even impossible, using the standard size specimens proposed in testing standards. Requirement to precisely position the specimens, even ones with subsize dimensions, and investigate mechanical properties of specific narrow HAZ regions presents certain challenge. This work investigates the X welded joint of S690QL1 grade high strength steel (HSS), welded with slightly overmatching filler metal. The material tensile properties are tested, using small scale specimens and indentation methods. Small scale specimens are ASTM E8 round tensile subsize and flat sheet mini tensile specimens (MTS). The indentation methods include hardness testing and profilometry-based indentation plastometry (PIP) method, to gain additional insights into material stress–strain behavior. Finally, paper evaluates the testing methods, comparatively processes the collected experimental data, and provides guidelines for heterogeneous structures testing.

Mechanically Adjustable 4-Channel RF Transceiver Coil Array for Rat Brain Imaging in a Whole-Body 7 T MR Scanner.

Investigations of human brain disorders are frequently conducted in rodent models using magnetic resonance imaging. Due to the small specimen size and the increase in signal-to-noise ratio with the static magnetic field strength, dedicated small-bore animal scanners can be used to acquire high-resolution data. Ultra-high-field (≥7 T) whole-body human scanners are increasingly available, and they can also be used for animal investigations. Dedicated sensors, in this case, radiofrequency coils, are required to achieve sufficient sensitivity for the high spatial resolution needed for imaging small anatomical structures. In this work, a four-channel transceiver coil array for rat brain imaging at 7 T is presented, which can be adjusted for use on a wide range of differently sized rats, from infants to large adults. Three suitable array designs (with two to four elements covering the whole rat brain) were compared using full-wave 3D electromagnetic simulation. An optimized static B1+ shim was derived to maximize B1+ in the rat brain for both small and big rats. The design, together with a 3D-printed adjustable coil housing, was tested and validated in ex vivo rat bench and MRI measurements.